Re: [PATCH] kvm: allow RO page when atomic && !write_fault

From: Lai Jiangshan
Date: Tue Feb 22 2011 - 03:24:06 EST


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@xxxxxxxxxxxxxx>
>> ---
>> 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)) {
>> --
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>
> --
> Gleb.
> --
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