Re: [PATCH v2 1/4] x86/xen: remove 32-bit Xen PV guest support
On 03.07.20 00:59, Boris Ostrovsky wrote:
On 7/1/20 7:06 AM, Juergen Gross wrote:
Xen is requiring 64-bit machines today and since Xen 4.14 it can be
built without 32-bit PV guest support. There is no need to carry the
burden of 32-bit PV guest support in the kernel any longer, as new
guests can be either HVM or PVH, or they can use a 64 bit kernel.
Remove the 32-bit Xen PV support from the kernel.
Signed-off-by: Juergen Gross
---
arch/x86/entry/entry_32.S | 109 +--
arch/x86/include/asm/proto.h | 2 +-
arch/x86/include/asm/segment.h | 2 +-
arch/x86/kernel/head_32.S | 31 ---
arch/x86/xen/Kconfig | 3 +-
arch/x86/xen/Makefile | 3 +-
arch/x86/xen/apic.c| 17 --
arch/x86/xen/enlighten_pv.c| 48 +
Should we drop PageHighMem() test in set_aliased_prot()?
(And there are few other places where is is used, in mmu_pv.c)
Yes, will drop those.
@@ -555,13 +547,8 @@ static void xen_load_tls(struct thread_struct *t, unsigned
int cpu)
* exception between the new %fs descriptor being loaded and
* %fs being effectively cleared at __switch_to().
*/
- if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
-#ifdef CONFIG_X86_32
- lazy_load_gs(0);
-#else
I think this also needs an adjustment to the preceding comment.
Yes.
-#ifdef CONFIG_X86_PAE
-static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
-{
- trace_xen_mmu_set_pte_atomic(ptep, pte);
- __xen_set_pte(ptep, pte);
Probably not for this series but I wonder whether __xen_set_pte() should
continue to use hypercall now that we are 64-bit only.
As Andrew wrote already the hypercall will be cheaper.
I'll adjust the comment, though.
@@ -654,14 +621,12 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t
*pgd,
Comment above should be updated.
Yes.
Juergen
Re: [PATCH v2 1/4] x86/xen: remove 32-bit Xen PV guest support
On 7/2/20 7:24 PM, Andrew Cooper wrote:
> On 02/07/2020 23:59, Boris Ostrovsky wrote:
>> On 7/1/20 7:06 AM, Juergen Gross wrote:
>>>
>>> -#ifdef CONFIG_X86_PAE
>>> -static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
>>> -{
>>> - trace_xen_mmu_set_pte_atomic(ptep, pte);
>>> - __xen_set_pte(ptep, pte);
>> Probably not for this series but I wonder whether __xen_set_pte() should
>> continue to use hypercall now that we are 64-bit only.
> The hypercall path is a SYSCALL (and SYSRET out).
>
> The "writeable" PTE path is a #PF, followed by an x86 instruction
> emulation, which then reaches the same logic as the hypercall path (and
> an IRET out).
Then we should at least update the comment.
-boris
Re: [PATCH v2 1/4] x86/xen: remove 32-bit Xen PV guest support
On 02/07/2020 23:59, Boris Ostrovsky wrote:
> On 7/1/20 7:06 AM, Juergen Gross wrote:
>>
>> -#ifdef CONFIG_X86_PAE
>> -static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
>> -{
>> -trace_xen_mmu_set_pte_atomic(ptep, pte);
>> -__xen_set_pte(ptep, pte);
>
> Probably not for this series but I wonder whether __xen_set_pte() should
> continue to use hypercall now that we are 64-bit only.
The hypercall path is a SYSCALL (and SYSRET out).
The "writeable" PTE path is a #PF, followed by an x86 instruction
emulation, which then reaches the same logic as the hypercall path (and
an IRET out).
~Andrew
Re: [PATCH v2 1/4] x86/xen: remove 32-bit Xen PV guest support
On 7/1/20 7:06 AM, Juergen Gross wrote:
> Xen is requiring 64-bit machines today and since Xen 4.14 it can be
> built without 32-bit PV guest support. There is no need to carry the
> burden of 32-bit PV guest support in the kernel any longer, as new
> guests can be either HVM or PVH, or they can use a 64 bit kernel.
>
> Remove the 32-bit Xen PV support from the kernel.
>
> Signed-off-by: Juergen Gross
> ---
> arch/x86/entry/entry_32.S | 109 +--
> arch/x86/include/asm/proto.h | 2 +-
> arch/x86/include/asm/segment.h | 2 +-
> arch/x86/kernel/head_32.S | 31 ---
> arch/x86/xen/Kconfig | 3 +-
> arch/x86/xen/Makefile | 3 +-
> arch/x86/xen/apic.c| 17 --
> arch/x86/xen/enlighten_pv.c| 48 +
Should we drop PageHighMem() test in set_aliased_prot()?
(And there are few other places where is is used, in mmu_pv.c)
> @@ -555,13 +547,8 @@ static void xen_load_tls(struct thread_struct *t,
> unsigned int cpu)
>* exception between the new %fs descriptor being loaded and
>* %fs being effectively cleared at __switch_to().
>*/
> - if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
> -#ifdef CONFIG_X86_32
> - lazy_load_gs(0);
> -#else
I think this also needs an adjustment to the preceding comment.
>
> -#ifdef CONFIG_X86_PAE
> -static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
> -{
> - trace_xen_mmu_set_pte_atomic(ptep, pte);
> - __xen_set_pte(ptep, pte);
Probably not for this series but I wonder whether __xen_set_pte() should
continue to use hypercall now that we are 64-bit only.
> @@ -654,14 +621,12 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t
> *pgd,
Comment above should be updated.
-boris
Re: [PATCH v2 1/4] x86/xen: remove 32-bit Xen PV guest support
On Wed, Jul 1, 2020 at 7:08 AM Juergen Gross wrote: > > Xen is requiring 64-bit machines today and since Xen 4.14 it can be > built without 32-bit PV guest support. There is no need to carry the > burden of 32-bit PV guest support in the kernel any longer, as new > guests can be either HVM or PVH, or they can use a 64 bit kernel. > > Remove the 32-bit Xen PV support from the kernel. If you send a v3, it would be better to split the move of the 64-bit code into xen-asm.S into a separate patch. -- Brian Gerst
