Re: [PATCH 1/1] KVM: PPC: Increase memslots to 320

[Thomas Huth]

On 09/12/15 04:28, Paul Mackerras wrote:
> On Wed, Nov 04, 2015 at 10:03:48AM +0100, Thomas Huth wrote:
>> Only using 32 memslots for KVM on powerpc is way too low, you can
>> nowadays hit this limit quite fast by adding a couple of PCI devices
>> and/or pluggable memory DIMMs to the guest.
>> x86 already increased the limit to 512 in total, to satisfy 256
>> pluggable DIMM slots, 3 private slots and 253 slots for other things
>> like PCI devices. On powerpc, we only have 32 pluggable DIMMs in
> 
> I agree with increasing the limit.  Is there a reason we have only 32
> pluggable DIMMs in QEMU on powerpc, not more?  Should we be increasing
> that limit too?  If so, maybe we should increase the number of memory
> slots to 512?

H ... the comment before the #define in QEMU reads:

/*
 * This defines the maximum number of DIMM slots we can have for sPAPR
 * guest. This is not defined by sPAPR but we are defining it to 32 slots
 * based on default number of slots provided by PowerPC kernel.
 */
#define SPAPR_MAX_RAM_SLOTS 32

So as far as I can see, there's indeed a possibility that we'll
increase this value once the kernel can handle more slots!

So I guess you're right and we should play save and use more slots
right from the start. I'll send a new patch with 512 instead.

>> QEMU, not 256, so we likely do not as much slots as on x86. Thus
> 
> "so we likely do not need as many slots as on x86" would be better
> English.

Oops, I'm sure that was my original intention ... anyway, thanks for
pointing it out, it's always good to get some feedback as a non-native
English speaker.

 Thomas

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[PATCH] KVM: PPC: Increase memslots to 512

[Thomas Huth]

Only using 32 memslots for KVM on powerpc is way too low, you can
nowadays hit this limit quite fast by adding a couple of PCI devices
and/or pluggable memory DIMMs to the guest.

x86 already increased the KVM_USER_MEM_SLOTS to 509, to satisfy 256
pluggable DIMM slots, 3 private slots and 253 slots for other things
like PCI devices (i.e. resulting in 256 + 3 + 253 = 512 slots in
total). We should do something similar for powerpc, and since we do
not use private slots here, we can set the value to 512 directly.

While we're at it, also remove the KVM_MEM_SLOTS_NUM definition
from the powerpc-specific header since this gets defined in the
generic kvm_host.h header anyway.

Signed-off-by: Thomas Huth 
---
 arch/powerpc/include/asm/kvm_host.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_host.h 
b/arch/powerpc/include/asm/kvm_host.h
index 887c259..2c96a72 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -38,8 +38,7 @@
 
 #define KVM_MAX_VCPUS  NR_CPUS
 #define KVM_MAX_VCORES NR_CPUS
-#define KVM_USER_MEM_SLOTS 32
-#define KVM_MEM_SLOTS_NUM KVM_USER_MEM_SLOTS
+#define KVM_USER_MEM_SLOTS 512
 
 #ifdef CONFIG_KVM_MMIO
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
-- 
1.8.3.1

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Re: [PATCH] KVM: PPC: Fix emulation of H_SET_DABR/X on POWER8

[Paul Mackerras]

On Fri, Nov 20, 2015 at 09:11:45AM +0100, Thomas Huth wrote:
> In the old DABR register, the BT (Breakpoint Translation) bit
> is bit number 61. In the new DAWRX register, the WT (Watchpoint
> Translation) bit is bit number 59. So to move the DABR-BT bit
> into the position of the DAWRX-WT bit, it has to be shifted by
> two, not only by one. This fixes hardware watchpoints in gdb of
> older guests that only use the H_SET_DABR/X interface instead
> of the new H_SET_MODE interface.
> 
> Signed-off-by: Thomas Huth 

Thanks, applied to my kvm-ppc-next branch, with cc: sta...@vger.kernel.org.

Paul.
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Re: [PATCH] kvm: remove unused variable 'vcpu_book3s'

[Paul Mackerras]

On Tue, Dec 01, 2015 at 08:42:10PM -0300, Geyslan G. Bem wrote:
> The vcpu_book3s struct is assigned but never used. So remove it.
> 
> Signed-off-by: Geyslan G. Bem 

Thanks, applied to my kvm-ppc-next branch.

Paul.
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Re: [PATCH] KVM: PPC: Increase memslots to 512

[Paul Mackerras]

On Wed, Dec 09, 2015 at 11:34:07AM +0100, Thomas Huth wrote:
> Only using 32 memslots for KVM on powerpc is way too low, you can
> nowadays hit this limit quite fast by adding a couple of PCI devices
> and/or pluggable memory DIMMs to the guest.
> 
> x86 already increased the KVM_USER_MEM_SLOTS to 509, to satisfy 256
> pluggable DIMM slots, 3 private slots and 253 slots for other things
> like PCI devices (i.e. resulting in 256 + 3 + 253 = 512 slots in
> total). We should do something similar for powerpc, and since we do
> not use private slots here, we can set the value to 512 directly.
> 
> While we're at it, also remove the KVM_MEM_SLOTS_NUM definition
> from the powerpc-specific header since this gets defined in the
> generic kvm_host.h header anyway.
> 
> Signed-off-by: Thomas Huth 

Thanks, applied to my kvm-ppc-next branch.

Paul.
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[GIT PULL] Please pull my kvm-ppc-fixes branch

[Paul Mackerras]

Hi Paolo,

I have a small patch that I would like to get into 4.4 because it
fixes a bug which for certain kernel configs allows userspace to crash
the kernel.  The configs are those for which KVM_BOOK3S_64_HV is set
(y or m) and KVM_BOOK3S_64_PR is not.  Fortunately most distros that
enable KVM_BOOK3S_64_HV also enable KVM_BOOK3S_64_PR, as far as I can
tell.

Thanks,
Paul.

The following changes since commit 09922076003ad66de41ea14d2f8c3b4a16ec7774:

  Merge tag 'kvm-arm-for-v4.4-rc4' of 
git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-master 
(2015-12-04 18:32:32 +0100)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc.git kvm-ppc-fixes

for you to fetch changes up to c20875a3e638e4a03e099b343ec798edd1af5cc6:

  KVM: PPC: Book3S HV: Prohibit setting illegal transaction state in MSR 
(2015-12-10 11:34:27 +1100)


Paul Mackerras (1):
  KVM: PPC: Book3S HV: Prohibit setting illegal transaction state in MSR

 arch/powerpc/kvm/book3s_hv.c | 6 ++
 1 file changed, 6 insertions(+)
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