Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On 16/06/15 15:19, Boris Ostrovsky wrote: > On 06/16/2015 10:15 AM, David Vrabel wrote: >> On 15/06/15 21:35, Ingo Molnar wrote: >>> * David Vrabel wrote: >>> On 15/06/15 10:05, Ian Campbell wrote: > On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: >> xen_mm_pin_all()/unpin_all() are used to implement full guest >> instance >> suspend/restore. It's a stop-all method that needs to iterate >> through all >> allocated pgds in the system to fix them up for Xen's use. >> >> This code uses pgd_list, probably because it was an easy interface. >> >> But we want to remove the pgd_list, so convert the code over to >> walk all >> tasks in the system. This is an equivalent method. It is not equivalent because pgd_alloc() now populates entries in pgds that are not visible to xen_mm_pin_all() (note how the original code adds the pgd to the pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly allocated page tables won't be correctly converted on suspend/resume and the new process will die after resume. >>> So how should the Xen logic be fixed for the new scheme? I can't say >>> I can see >>> through the paravirt complexity here. >> Actually, since we freeze_processes() before trying to pin page tables, >> I think it should be ok as-is. >> >> I'll put the patch through some tests. > > Actually, I just ran this through a couple of boot/suspend/resume tests > and didn't see any issues (with the one fix I mentioned to Ingo > earlier). On unstable Xen only. In which case this can have a: Reviewed-by: David Vrabel Thanks. David ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On 06/16/2015 10:15 AM, David Vrabel wrote: On 15/06/15 21:35, Ingo Molnar wrote: * David Vrabel wrote: On 15/06/15 10:05, Ian Campbell wrote: On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: xen_mm_pin_all()/unpin_all() are used to implement full guest instance suspend/restore. It's a stop-all method that needs to iterate through all allocated pgds in the system to fix them up for Xen's use. This code uses pgd_list, probably because it was an easy interface. But we want to remove the pgd_list, so convert the code over to walk all tasks in the system. This is an equivalent method. It is not equivalent because pgd_alloc() now populates entries in pgds that are not visible to xen_mm_pin_all() (note how the original code adds the pgd to the pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly allocated page tables won't be correctly converted on suspend/resume and the new process will die after resume. So how should the Xen logic be fixed for the new scheme? I can't say I can see through the paravirt complexity here. Actually, since we freeze_processes() before trying to pin page tables, I think it should be ok as-is. I'll put the patch through some tests. Actually, I just ran this through a couple of boot/suspend/resume tests and didn't see any issues (with the one fix I mentioned to Ingo earlier). On unstable Xen only. -boris ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On 15/06/15 21:35, Ingo Molnar wrote: > > * David Vrabel wrote: > >> On 15/06/15 10:05, Ian Campbell wrote: >>> On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: > xen_mm_pin_all()/unpin_all() are used to implement full guest instance suspend/restore. It's a stop-all method that needs to iterate through all allocated pgds in the system to fix them up for Xen's use. This code uses pgd_list, probably because it was an easy interface. But we want to remove the pgd_list, so convert the code over to walk all tasks in the system. This is an equivalent method. >> >> It is not equivalent because pgd_alloc() now populates entries in pgds that >> are >> not visible to xen_mm_pin_all() (note how the original code adds the pgd to >> the >> pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly >> allocated page tables won't be correctly converted on suspend/resume and the >> new >> process will die after resume. > > So how should the Xen logic be fixed for the new scheme? I can't say I can > see > through the paravirt complexity here. Actually, since we freeze_processes() before trying to pin page tables, I think it should be ok as-is. I'll put the patch through some tests. David ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
* David Vrabel wrote: > On 15/06/15 10:05, Ian Campbell wrote: > > On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: > >> xen_mm_pin_all()/unpin_all() are used to implement full guest instance > >> suspend/restore. It's a stop-all method that needs to iterate through all > >> allocated pgds in the system to fix them up for Xen's use. > >> > >> This code uses pgd_list, probably because it was an easy interface. > >> > >> But we want to remove the pgd_list, so convert the code over to walk all > >> tasks in the system. This is an equivalent method. > > It is not equivalent because pgd_alloc() now populates entries in pgds that > are > not visible to xen_mm_pin_all() (note how the original code adds the pgd to > the > pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly > allocated page tables won't be correctly converted on suspend/resume and the > new > process will die after resume. So how should the Xen logic be fixed for the new scheme? I can't say I can see through the paravirt complexity here. Thanks, Ingo ___ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On 15/06/15 10:05, Ian Campbell wrote:
> On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote:
>> xen_mm_pin_all()/unpin_all() are used to implement full guest instance
>> suspend/restore. It's a stop-all method that needs to iterate through
>> all allocated pgds in the system to fix them up for Xen's use.
>>
>> This code uses pgd_list, probably because it was an easy interface.
>>
>> But we want to remove the pgd_list, so convert the code over to walk
>> all tasks in the system. This is an equivalent method.
It is not equivalent because pgd_alloc() now populates entries in pgds
that are not visible to xen_mm_pin_all() (note how the original code
adds the pgd to the pgd_list in pgd_ctor() before calling
pgd_prepopulate_pmd()). These newly allocated page tables won't be
correctly converted on suspend/resume and the new process will die after
resume.
David
>>
>> (As I don't use Xen this is was only build tested.)
>
> In which case it seems extra important to copy the appropriate
> maintainers, which I've done here.
>
> Ian.
>
>>
>> Cc: Andrew Morton
>> Cc: Andy Lutomirski
>> Cc: Borislav Petkov
>> Cc: Brian Gerst
>> Cc: Denys Vlasenko
>> Cc: H. Peter Anvin
>> Cc: Linus Torvalds
>> Cc: Oleg Nesterov
>> Cc: Peter Zijlstra
>> Cc: Thomas Gleixner
>> Cc: Waiman Long
>> Cc: linux...@kvack.org
>> Signed-off-by: Ingo Molnar
>> ---
>> arch/x86/xen/mmu.c | 51 ++-
>> 1 file changed, 38 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
>> index dd151b2045b0..70a3df5b0b54 100644
>> --- a/arch/x86/xen/mmu.c
>> +++ b/arch/x86/xen/mmu.c
>> @@ -853,15 +853,27 @@ static void xen_pgd_pin(struct mm_struct *mm)
>> */
>> void xen_mm_pin_all(void)
>> {
>> -struct page *page;
>> +struct task_struct *g, *p;
>>
>> -spin_lock(&pgd_lock);
>> +spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list
>> iteration: */
>>
>> -list_for_each_entry(page, &pgd_list, lru) {
>> -if (!PagePinned(page)) {
>> -__xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
>> -SetPageSavePinned(page);
>> +for_each_process_thread(g, p) {
>> +struct mm_struct *mm;
>> +struct page *page;
>> +pgd_t *pgd;
>> +
>> +task_lock(p);
>> +mm = p->mm;
>> +if (mm) {
>> +pgd = mm->pgd;
>> +page = virt_to_page(pgd);
>> +
>> +if (!PagePinned(page)) {
>> +__xen_pgd_pin(&init_mm, pgd);
>> +SetPageSavePinned(page);
>> +}
>> }
>> +task_unlock(p);
>> }
>>
>> spin_unlock(&pgd_lock);
>> @@ -967,19 +979,32 @@ static void xen_pgd_unpin(struct mm_struct *mm)
>> */
>> void xen_mm_unpin_all(void)
>> {
>> -struct page *page;
>> +struct task_struct *g, *p;
>>
>> -spin_lock(&pgd_lock);
>> +spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list
>> iteration: */
>>
>> -list_for_each_entry(page, &pgd_list, lru) {
>> -if (PageSavePinned(page)) {
>> -BUG_ON(!PagePinned(page));
>> -__xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
>> -ClearPageSavePinned(page);
>> +for_each_process_thread(g, p) {
>> +struct mm_struct *mm;
>> +struct page *page;
>> +pgd_t *pgd;
>> +
>> +task_lock(p);
>> +mm = p->mm;
>> +if (mm) {
>> +pgd = mm->pgd;
>> +page = virt_to_page(pgd);
>> +
>> +if (PageSavePinned(page)) {
>> +BUG_ON(!PagePinned(page));
>> +__xen_pgd_unpin(&init_mm, pgd);
>> +ClearPageSavePinned(page);
>> +}
>> }
>> +task_unlock(p);
>> }
>>
>> spin_unlock(&pgd_lock);
>> +rcu_read_unlock();
>> }
>>
>> static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
>
>
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Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code
On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote:
> xen_mm_pin_all()/unpin_all() are used to implement full guest instance
> suspend/restore. It's a stop-all method that needs to iterate through
> all allocated pgds in the system to fix them up for Xen's use.
>
> This code uses pgd_list, probably because it was an easy interface.
>
> But we want to remove the pgd_list, so convert the code over to walk
> all tasks in the system. This is an equivalent method.
>
> (As I don't use Xen this is was only build tested.)
In which case it seems extra important to copy the appropriate
maintainers, which I've done here.
Ian.
>
> Cc: Andrew Morton
> Cc: Andy Lutomirski
> Cc: Borislav Petkov
> Cc: Brian Gerst
> Cc: Denys Vlasenko
> Cc: H. Peter Anvin
> Cc: Linus Torvalds
> Cc: Oleg Nesterov
> Cc: Peter Zijlstra
> Cc: Thomas Gleixner
> Cc: Waiman Long
> Cc: linux...@kvack.org
> Signed-off-by: Ingo Molnar
> ---
> arch/x86/xen/mmu.c | 51 ++-
> 1 file changed, 38 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index dd151b2045b0..70a3df5b0b54 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -853,15 +853,27 @@ static void xen_pgd_pin(struct mm_struct *mm)
> */
> void xen_mm_pin_all(void)
> {
> - struct page *page;
> + struct task_struct *g, *p;
>
> - spin_lock(&pgd_lock);
> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list
> iteration: */
>
> - list_for_each_entry(page, &pgd_list, lru) {
> - if (!PagePinned(page)) {
> - __xen_pgd_pin(&init_mm, (pgd_t *)page_address(page));
> - SetPageSavePinned(page);
> + for_each_process_thread(g, p) {
> + struct mm_struct *mm;
> + struct page *page;
> + pgd_t *pgd;
> +
> + task_lock(p);
> + mm = p->mm;
> + if (mm) {
> + pgd = mm->pgd;
> + page = virt_to_page(pgd);
> +
> + if (!PagePinned(page)) {
> + __xen_pgd_pin(&init_mm, pgd);
> + SetPageSavePinned(page);
> + }
> }
> + task_unlock(p);
> }
>
> spin_unlock(&pgd_lock);
> @@ -967,19 +979,32 @@ static void xen_pgd_unpin(struct mm_struct *mm)
> */
> void xen_mm_unpin_all(void)
> {
> - struct page *page;
> + struct task_struct *g, *p;
>
> - spin_lock(&pgd_lock);
> + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list
> iteration: */
>
> - list_for_each_entry(page, &pgd_list, lru) {
> - if (PageSavePinned(page)) {
> - BUG_ON(!PagePinned(page));
> - __xen_pgd_unpin(&init_mm, (pgd_t *)page_address(page));
> - ClearPageSavePinned(page);
> + for_each_process_thread(g, p) {
> + struct mm_struct *mm;
> + struct page *page;
> + pgd_t *pgd;
> +
> + task_lock(p);
> + mm = p->mm;
> + if (mm) {
> + pgd = mm->pgd;
> + page = virt_to_page(pgd);
> +
> + if (PageSavePinned(page)) {
> + BUG_ON(!PagePinned(page));
> + __xen_pgd_unpin(&init_mm, pgd);
> + ClearPageSavePinned(page);
> + }
> }
> + task_unlock(p);
> }
>
> spin_unlock(&pgd_lock);
> + rcu_read_unlock();
> }
>
> static void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)
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