* [PATCH] kvm: allow RO page when atomic && !write_fault
@ 2011-02-21 3:47 Lai Jiangshan
2011-02-21 9:47 ` Gleb Natapov
2011-02-22 19:24 ` Marcelo Tosatti
0 siblings, 2 replies; 4+ messages in thread
From: Lai Jiangshan @ 2011-02-21 3:47 UTC (permalink / raw)
To: kvm@vger.kernel.org, LKML, Avi Kivity, Marcelo Tosatti
Atomic-able hva_to_pfn() patches and allow-read-only-page patches
are merged almost the same time. But hva_to_pfn() does not handle
these two issues well together.
When @atomic && !@write_fault && host-is-read-only-page-mapped
the code will return fault_page, actually, it will be better
if we return the pfn of the read-only-page.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1fa0d29..f49cfc0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1060,31 +1060,27 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
BUG_ON(!write_fault && !writable);
if (writable)
- *writable = true;
+ *writable = write_fault;
if (atomic || async)
- npages = __get_user_pages_fast(addr, 1, 1, page);
+ npages = __get_user_pages_fast(addr, 1, write_fault, page);
if (unlikely(npages != 1) && !atomic) {
might_sleep();
-
- if (writable)
- *writable = write_fault;
-
npages = get_user_pages_fast(addr, 1, write_fault, page);
+ }
- /* map read fault as writable if possible */
- if (unlikely(!write_fault) && npages == 1) {
- struct page *wpage[1];
+ /* map read fault as writable if possible */
+ if (unlikely(!write_fault) && npages == 1) {
+ struct page *wpage[1];
- npages = __get_user_pages_fast(addr, 1, 1, wpage);
- if (npages == 1) {
- *writable = true;
- put_page(page[0]);
- page[0] = wpage[0];
- }
- npages = 1;
+ npages = __get_user_pages_fast(addr, 1, 1, wpage);
+ if (npages == 1) {
+ *writable = true;
+ put_page(page[0]);
+ page[0] = wpage[0];
}
+ npages = 1;
}
if (unlikely(npages != 1)) {
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] kvm: allow RO page when atomic && !write_fault
2011-02-21 3:47 [PATCH] kvm: allow RO page when atomic && !write_fault Lai Jiangshan
@ 2011-02-21 9:47 ` Gleb Natapov
2011-02-22 8:24 ` Lai Jiangshan
2011-02-22 19:24 ` Marcelo Tosatti
1 sibling, 1 reply; 4+ messages in thread
From: Gleb Natapov @ 2011-02-21 9:47 UTC (permalink / raw)
To: Lai Jiangshan; +Cc: kvm@vger.kernel.org, LKML, Avi Kivity, Marcelo Tosatti
On Mon, Feb 21, 2011 at 11:47:36AM +0800, Lai Jiangshan wrote:
>
> Atomic-able hva_to_pfn() patches and allow-read-only-page patches
> are merged almost the same time. But hva_to_pfn() does not handle
> these two issues well together.
>
> When @atomic && !@write_fault && host-is-read-only-page-mapped
> the code will return fault_page, actually, it will be better
> if we return the pfn of the read-only-page.
>
This patch will conflict with not yet applied https://lkml.org/lkml/2011/2/1/94
What it the status of that patch?
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1fa0d29..f49cfc0 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1060,31 +1060,27 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
> BUG_ON(!write_fault && !writable);
>
> if (writable)
> - *writable = true;
> + *writable = write_fault;
>
> if (atomic || async)
> - npages = __get_user_pages_fast(addr, 1, 1, page);
> + npages = __get_user_pages_fast(addr, 1, write_fault, page);
>
> if (unlikely(npages != 1) && !atomic) {
> might_sleep();
> -
> - if (writable)
> - *writable = write_fault;
> -
> npages = get_user_pages_fast(addr, 1, write_fault, page);
> + }
>
> - /* map read fault as writable if possible */
> - if (unlikely(!write_fault) && npages == 1) {
> - struct page *wpage[1];
> + /* map read fault as writable if possible */
> + if (unlikely(!write_fault) && npages == 1) {
> + struct page *wpage[1];
>
> - npages = __get_user_pages_fast(addr, 1, 1, wpage);
> - if (npages == 1) {
> - *writable = true;
> - put_page(page[0]);
> - page[0] = wpage[0];
> - }
> - npages = 1;
> + npages = __get_user_pages_fast(addr, 1, 1, wpage);
> + if (npages == 1) {
> + *writable = true;
> + put_page(page[0]);
> + page[0] = wpage[0];
> }
> + npages = 1;
> }
>
> if (unlikely(npages != 1)) {
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Gleb.
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] kvm: allow RO page when atomic && !write_fault
2011-02-21 9:47 ` Gleb Natapov
@ 2011-02-22 8:24 ` Lai Jiangshan
0 siblings, 0 replies; 4+ messages in thread
From: Lai Jiangshan @ 2011-02-22 8:24 UTC (permalink / raw)
To: Gleb Natapov; +Cc: kvm@vger.kernel.org, LKML, Avi Kivity, Marcelo Tosatti
On 02/21/2011 05:47 PM, Gleb Natapov wrote:
> On Mon, Feb 21, 2011 at 11:47:36AM +0800, Lai Jiangshan wrote:
>>
>> Atomic-able hva_to_pfn() patches and allow-read-only-page patches
>> are merged almost the same time. But hva_to_pfn() does not handle
>> these two issues well together.
>>
>> When @atomic && !@write_fault && host-is-read-only-page-mapped
>> the code will return fault_page, actually, it will be better
>> if we return the pfn of the read-only-page.
>>
> This patch will conflict with not yet applied https://lkml.org/lkml/2011/2/1/94
> What it the status of that patch?
I will update/resend this patch after the patch you referred applied.
Thanks,
Lai
>
>> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
>> ---
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 1fa0d29..f49cfc0 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -1060,31 +1060,27 @@ static pfn_t hva_to_pfn(struct kvm *kvm, unsigned long addr, bool atomic,
>> BUG_ON(!write_fault && !writable);
>>
>> if (writable)
>> - *writable = true;
>> + *writable = write_fault;
>>
>> if (atomic || async)
>> - npages = __get_user_pages_fast(addr, 1, 1, page);
>> + npages = __get_user_pages_fast(addr, 1, write_fault, page);
>>
>> if (unlikely(npages != 1) && !atomic) {
>> might_sleep();
>> -
>> - if (writable)
>> - *writable = write_fault;
>> -
>> npages = get_user_pages_fast(addr, 1, write_fault, page);
>> + }
>>
>> - /* map read fault as writable if possible */
>> - if (unlikely(!write_fault) && npages == 1) {
>> - struct page *wpage[1];
>> + /* map read fault as writable if possible */
>> + if (unlikely(!write_fault) && npages == 1) {
>> + struct page *wpage[1];
>>
>> - npages = __get_user_pages_fast(addr, 1, 1, wpage);
>> - if (npages == 1) {
>> - *writable = true;
>> - put_page(page[0]);
>> - page[0] = wpage[0];
>> - }
>> - npages = 1;
>> + npages = __get_user_pages_fast(addr, 1, 1, wpage);
>> + if (npages == 1) {
>> + *writable = true;
>> + put_page(page[0]);
>> + page[0] = wpage[0];
>> }
>> + npages = 1;
>> }
>>
>> if (unlikely(npages != 1)) {
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>
> --
> Gleb.
> --
> To unsubscribe from this list: send the line "unsubscribe kvm" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] kvm: allow RO page when atomic && !write_fault
2011-02-21 3:47 [PATCH] kvm: allow RO page when atomic && !write_fault Lai Jiangshan
2011-02-21 9:47 ` Gleb Natapov
@ 2011-02-22 19:24 ` Marcelo Tosatti
1 sibling, 0 replies; 4+ messages in thread
From: Marcelo Tosatti @ 2011-02-22 19:24 UTC (permalink / raw)
To: Lai Jiangshan; +Cc: kvm@vger.kernel.org, LKML, Avi Kivity
On Mon, Feb 21, 2011 at 11:47:36AM +0800, Lai Jiangshan wrote:
>
> Atomic-able hva_to_pfn() patches and allow-read-only-page patches
> are merged almost the same time. But hva_to_pfn() does not handle
> these two issues well together.
>
> When @atomic && !@write_fault && host-is-read-only-page-mapped
> the code will return fault_page, actually, it will be better
> if we return the pfn of the read-only-page.
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Lai,
For pte prefetch, user of atomic hva_to_pfn, the write_fault parameter
is meaningless (since that information is only available for the pte
being faulted).
Returning fault page for a read-only page is useful so that pte prefetch
is aborted.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-02-21 3:47 [PATCH] kvm: allow RO page when atomic && !write_fault Lai Jiangshan
2011-02-21 9:47 ` Gleb Natapov
2011-02-22 8:24 ` Lai Jiangshan
2011-02-22 19:24 ` Marcelo Tosatti
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