* Re: [RFC PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages
[not found] ` <4BDA4342.9070603@cn.fujitsu.com>
@ 2010-05-07 8:52 ` Lai Jiangshan
2010-05-10 8:55 ` Avi Kivity
1 sibling, 0 replies; 4+ messages in thread
From: Lai Jiangshan @ 2010-05-07 8:52 UTC (permalink / raw)
To: Lai Jiangshan, Avi Kivity, Marcelo Tosatti
Cc: Joerg Roedel, LKML, kvm, Gui Jianfeng
Lai Jiangshan wrote:
> Lai Jiangshan wrote:
>> RFC, because maybe I missing something with the old code.
>>
>> Frome: Lai Jiangshan <laijs@cn.fujitsu.com>
>>
>> In Document/kvm/mmu.txt:
>> gfn:
>> Either the guest page table containing the translations shadowed by this
>> page, or the base page frame for linear translations. See role.direct.
>>
>> But in function FNAME(fetch)(), sp->gfn is incorrect when one of following
>> situations occurred:
>> 1) guest is 32bit paging and guest uses pse-36 and the guest PDE maps
>> a 4-MByte page(backed by 4k host pages) and bits 20:13 of the guest PDE
>> is not equals to 0.
>> 2) guest is long mode paging and the guest PDPTE maps a 1-GByte page
>> (backed by 4k or 2M host pages)
>>
>
> Resend this patch with the changelog changed.
>
> As Marcelo Tosatti and Gui Jianfeng points out,
> FNAME(fetch)() miss quadrant on 4mb large page emulation with shadow.
>
> Subject: [PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages
>
> In Document/kvm/mmu.txt:
> gfn:
> Either the guest page table containing the translations shadowed by this
> page, or the base page frame for linear translations. See role.direct.
>
> But in function FNAME(fetch)(), sp->gfn is incorrect when one of following
> situations occurred:
> 1) guest is 32bit paging and the guest PDE maps a 4-MByte page
> (backed by 4k host pages), FNAME(fetch)() miss handling the quadrant.
>
> And if guest use pse-36, "table_gfn = gpte_to_gfn(gw->ptes[level - delta]);"
> is incorrect.
> 2) guest is long mode paging and the guest PDPTE maps a 1-GByte page
> (backed by 4k or 2M host pages).
>
> So we fix it to suit to the document and suit to the code which
> requires sp->gfn correct when sp->role.direct=1.
>
> We use the goal mapping gfn(gw->gfn) to calculate the base page frame
> for linear translations, it is simple and easy to be understood.
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
Could you add these:
Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Reported-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Thanks.
Lai.
PS.
The whole patches includes:
[PATCH] kvm mmu: reduce 50% memory usage
[PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages
[PATCH] kvm, tdp: calculate correct base gfn for non-DIR level
[PATCH] kvm: update document of gfns
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [RFC PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages
[not found] ` <4BDA4342.9070603@cn.fujitsu.com>
2010-05-07 8:52 ` [RFC PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages Lai Jiangshan
@ 2010-05-10 8:55 ` Avi Kivity
1 sibling, 0 replies; 4+ messages in thread
From: Avi Kivity @ 2010-05-10 8:55 UTC (permalink / raw)
To: Lai Jiangshan; +Cc: Marcelo Tosatti, Joerg Roedel, LKML, kvm
On 04/30/2010 05:41 AM, Lai Jiangshan wrote:
> Lai Jiangshan wrote:
>
>> RFC, because maybe I missing something with the old code.
>>
>> Frome: Lai Jiangshan<laijs@cn.fujitsu.com>
>>
>> In Document/kvm/mmu.txt:
>> gfn:
>> Either the guest page table containing the translations shadowed by this
>> page, or the base page frame for linear translations. See role.direct.
>>
>> But in function FNAME(fetch)(), sp->gfn is incorrect when one of following
>> situations occurred:
>> 1) guest is 32bit paging and guest uses pse-36 and the guest PDE maps
>> a 4-MByte page(backed by 4k host pages) and bits 20:13 of the guest PDE
>> is not equals to 0.
>> 2) guest is long mode paging and the guest PDPTE maps a 1-GByte page
>> (backed by 4k or 2M host pages)
>>
>>
> Resend this patch with the changelog changed.
>
> As Marcelo Tosatti and Gui Jianfeng points out,
> FNAME(fetch)() miss quadrant on 4mb large page emulation with shadow.
>
> Subject: [PATCH] kvm: calculate correct gfn for small host pages which emulates large guest pages
>
> In Document/kvm/mmu.txt:
> gfn:
> Either the guest page table containing the translations shadowed by this
> page, or the base page frame for linear translations. See role.direct.
>
> But in function FNAME(fetch)(), sp->gfn is incorrect when one of following
> situations occurred:
> 1) guest is 32bit paging and the guest PDE maps a 4-MByte page
> (backed by 4k host pages), FNAME(fetch)() miss handling the quadrant.
>
> And if guest use pse-36, "table_gfn = gpte_to_gfn(gw->ptes[level - delta]);"
> is incorrect.
> 2) guest is long mode paging and the guest PDPTE maps a 1-GByte page
> (backed by 4k or 2M host pages).
>
> So we fix it to suit to the document and suit to the code which
> requires sp->gfn correct when sp->role.direct=1.
>
> We use the goal mapping gfn(gw->gfn) to calculate the base page frame
> for linear translations, it is simple and easy to be understood.
>
> Signed-off-by: Lai Jiangshan<laijs@cn.fujitsu.com>
> ---
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 702c016..958e9c6 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -338,10 +338,13 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
> direct = 1;
> if (!is_dirty_gpte(gw->ptes[level - delta]))
> access&= ~ACC_WRITE_MASK;
> - table_gfn = gpte_to_gfn(gw->ptes[level - delta]);
> - /* advance table_gfn when emulating 1gb pages with 4k */
> - if (delta == 0)
> - table_gfn += PT_INDEX(addr, level);
> + /*
> + * It is a large guest pages backed by small host pages,
> + * So we set @direct(@shadow_page->role.direct)=1, and
> + * set @table_gfn(@shadow_page->gfn)=the base page frame
> + * for linear translations.
> + */
> + table_gfn = gw->gfn& ~(KVM_PAGES_PER_HPAGE(level) - 1);
> } else {
> direct = 0;
> table_gfn = gw->table_gfn[level - 2];
>
Looks good, indeed it is a lot easier to understand than the original
calculation (a minor issue is that the variable name is misleading, but
that's a problem with kvm_mmu_page definition and not this patch).
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 4+ messages in thread