2024-02-27 23:22:17

by Paolo Bonzini

Subject: [PATCH 02/21] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values

From: Sean Christopherson <[email protected]>

Add support to MMU caches for initializing a page with a custom 64-bit
value, e.g. to pre-fill an entire page table with non-zero PTE values.
The functionality will be used by x86 to support Intel's TDX, which needs
to set bit 63 in all non-present PTEs in order to prevent !PRESENT page
faults from getting reflected into the guest (Intel's EPT Violation #VE
architecture made the less than brilliant decision of having the per-PTE
behavior be opt-out instead of opt-in).

Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Isaku Yamahata <[email protected]>
Message-Id: <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <[email protected]>
---
include/linux/kvm_types.h | 1 +
virt/kvm/kvm_main.c | 16 ++++++++++++++--
2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index d93f6522b2c3..827ecc0b7e10 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -86,6 +86,7 @@ struct gfn_to_pfn_cache {
struct kvm_mmu_memory_cache {
gfp_t gfp_zero;
gfp_t gfp_custom;
+ u64 init_value;
struct kmem_cache *kmem_cache;
int capacity;
int nobjs;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9c99c9373a3e..c9828feb7a1c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -401,12 +401,17 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
gfp_t gfp_flags)
{
+ void *page;
+
gfp_flags |= mc->gfp_zero;

if (mc->kmem_cache)
return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
- else
- return (void *)__get_free_page(gfp_flags);
+
+ page = (void *)__get_free_page(gfp_flags);
+ if (page && mc->init_value)
+ memset64(page, mc->init_value, PAGE_SIZE / sizeof(mc->init_value));
+ return page;
}

int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
@@ -421,6 +426,13 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
if (WARN_ON_ONCE(!capacity))
return -EIO;

+ /*
+ * Custom init values can be used only for page allocations,
+ * and obviously conflict with __GFP_ZERO.
+ */
+ if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache || mc->gfp_zero)))
+ return -EIO;
+
mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
if (!mc->objects)
return -ENOMEM;
--
2.39.0

2024-02-29 13:47:05

by Xiaoyao Li

Subject: Re: [PATCH 02/21] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values

On 2/28/2024 7:20 AM, Paolo Bonzini wrote:
> From: Sean Christopherson <[email protected]>
>
> Add support to MMU caches for initializing a page with a custom 64-bit
> value, e.g. to pre-fill an entire page table with non-zero PTE values.
> The functionality will be used by x86 to support Intel's TDX, which needs
> to set bit 63 in all non-present PTEs in order to prevent !PRESENT page
> faults from getting reflected into the guest (Intel's EPT Violation #VE
> architecture made the less than brilliant decision of having the per-PTE
> behavior be opt-out instead of opt-in).
>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Isaku Yamahata <[email protected]>
> Message-Id: <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
> Signed-off-by: Paolo Bonzini <[email protected]>

Reviewed-by: Xiaoyao Li <[email protected]>

> ---
> include/linux/kvm_types.h | 1 +
> virt/kvm/kvm_main.c | 16 ++++++++++++++--
> 2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index d93f6522b2c3..827ecc0b7e10 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -86,6 +86,7 @@ struct gfn_to_pfn_cache {
> struct kvm_mmu_memory_cache {
> gfp_t gfp_zero;
> gfp_t gfp_custom;
> + u64 init_value;
> struct kmem_cache *kmem_cache;
> int capacity;
> int nobjs;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 9c99c9373a3e..c9828feb7a1c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -401,12 +401,17 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
> static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
> gfp_t gfp_flags)
> {
> + void *page;
> +
> gfp_flags |= mc->gfp_zero;
>
> if (mc->kmem_cache)
> return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
> - else
> - return (void *)__get_free_page(gfp_flags);
> +
> + page = (void *)__get_free_page(gfp_flags);
> + if (page && mc->init_value)
> + memset64(page, mc->init_value, PAGE_SIZE / sizeof(mc->init_value));
> + return page;
> }
>
> int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
> @@ -421,6 +426,13 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
> if (WARN_ON_ONCE(!capacity))
> return -EIO;
>
> + /*
> + * Custom init values can be used only for page allocations,
> + * and obviously conflict with __GFP_ZERO.
> + */
> + if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache || mc->gfp_zero)))
> + return -EIO;
> +
> mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
> if (!mc->objects)
> return -ENOMEM;

2024-03-05 06:56:05

by Binbin Wu

Subject: Re: [PATCH 02/21] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values

On 2/28/2024 7:20 AM, Paolo Bonzini wrote:
> From: Sean Christopherson <[email protected]>
>
> Add support to MMU caches for initializing a page with a custom 64-bit
> value, e.g. to pre-fill an entire page table with non-zero PTE values.
> The functionality will be used by x86 to support Intel's TDX, which needs
> to set bit 63 in all non-present PTEs in order to prevent !PRESENT page
> faults from getting reflected into the guest (Intel's EPT Violation #VE
> architecture made the less than brilliant decision of having the per-PTE
> behavior be opt-out instead of opt-in).
>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Isaku Yamahata <[email protected]>
> Message-Id: <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
> Signed-off-by: Paolo Bonzini <[email protected]>
> ---
> include/linux/kvm_types.h | 1 +
> virt/kvm/kvm_main.c | 16 ++++++++++++++--
> 2 files changed, 15 insertions(+), 2 deletions(-)

Reviewed-by: Binbin Wu <[email protected]>

>
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index d93f6522b2c3..827ecc0b7e10 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -86,6 +86,7 @@ struct gfn_to_pfn_cache {
> struct kvm_mmu_memory_cache {
> gfp_t gfp_zero;
> gfp_t gfp_custom;
> + u64 init_value;
> struct kmem_cache *kmem_cache;
> int capacity;
> int nobjs;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 9c99c9373a3e..c9828feb7a1c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -401,12 +401,17 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
> static inline void *mmu_memory_cache_alloc_obj(struct kvm_mmu_memory_cache *mc,
> gfp_t gfp_flags)
> {
> + void *page;
> +
> gfp_flags |= mc->gfp_zero;
>
> if (mc->kmem_cache)
> return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
> - else
> - return (void *)__get_free_page(gfp_flags);
> +
> + page = (void *)__get_free_page(gfp_flags);
> + if (page && mc->init_value)
> + memset64(page, mc->init_value, PAGE_SIZE / sizeof(mc->init_value));
> + return page;
> }
>
> int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity, int min)
> @@ -421,6 +426,13 @@ int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int capacity,
> if (WARN_ON_ONCE(!capacity))
> return -EIO;
>
> + /*
> + * Custom init values can be used only for page allocations,
> + * and obviously conflict with __GFP_ZERO.
> + */
> + if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache || mc->gfp_zero)))
> + return -EIO;
> +
> mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
> if (!mc->objects)
> return -ENOMEM;

2024-03-26 19:02:41

by Binbin Wu

Subject: Re: [PATCH 02/21] KVM: Allow page-sized MMU caches to be initialized with custom 64-bit values

On 3/5/2024 2:55 PM, Binbin Wu wrote:
>
>
> On 2/28/2024 7:20 AM, Paolo Bonzini wrote:
>> From: Sean Christopherson <[email protected]>
>>
>> Add support to MMU caches for initializing a page with a custom 64-bit
>> value, e.g. to pre-fill an entire page table with non-zero PTE values.
>> The functionality will be used by x86 to support Intel's TDX, which
>> needs
>> to set bit 63 in all non-present PTEs in order to prevent !PRESENT page
>> faults from getting reflected into the guest (Intel's EPT Violation #VE
>> architecture made the less than brilliant decision of having the per-PTE
>> behavior be opt-out instead of opt-in).
>>
>> Signed-off-by: Sean Christopherson <[email protected]>
>> Signed-off-by: Isaku Yamahata <[email protected]>
>> Message-Id:
>> <5919f685f109a1b0ebc6bd8fc4536ee94bcc172d.1705965635.git.isaku.yamahata@intel.com>
>> Signed-off-by: Paolo Bonzini <[email protected]>
>> ---
>>   include/linux/kvm_types.h |  1 +
>>   virt/kvm/kvm_main.c       | 16 ++++++++++++++--
>>   2 files changed, 15 insertions(+), 2 deletions(-)
>
> Reviewed-by: Binbin Wu <[email protected]>
>
>>
>> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
>> index d93f6522b2c3..827ecc0b7e10 100644
>> --- a/include/linux/kvm_types.h
>> +++ b/include/linux/kvm_types.h
>> @@ -86,6 +86,7 @@ struct gfn_to_pfn_cache {
>>   struct kvm_mmu_memory_cache {
>>       gfp_t gfp_zero;
>>       gfp_t gfp_custom;
>> +    u64 init_value;
>>       struct kmem_cache *kmem_cache;
>>       int capacity;
>>       int nobjs;
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 9c99c9373a3e..c9828feb7a1c 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -401,12 +401,17 @@ static void kvm_flush_shadow_all(struct kvm *kvm)
>>   static inline void *mmu_memory_cache_alloc_obj(struct
>> kvm_mmu_memory_cache *mc,
>>                              gfp_t gfp_flags)
>>   {
>> +    void *page;
>> +
>>       gfp_flags |= mc->gfp_zero;
>>         if (mc->kmem_cache)
>>           return kmem_cache_alloc(mc->kmem_cache, gfp_flags);
>> -    else
>> -        return (void *)__get_free_page(gfp_flags);
>> +
>> +    page = (void *)__get_free_page(gfp_flags);
>> +    if (page && mc->init_value)
>> +        memset64(page, mc->init_value, PAGE_SIZE /
>> sizeof(mc->init_value));

Do we need a static_assert() to make sure mc->init_value is 64bit?

>> +    return page;
>>   }
>>     int __kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc,
>> int capacity, int min)
>> @@ -421,6 +426,13 @@ int __kvm_mmu_topup_memory_cache(struct
>> kvm_mmu_memory_cache *mc, int capacity,
>>           if (WARN_ON_ONCE(!capacity))
>>               return -EIO;
>>   +        /*
>> +         * Custom init values can be used only for page allocations,
>> +         * and obviously conflict with __GFP_ZERO.
>> +         */
>> +        if (WARN_ON_ONCE(mc->init_value && (mc->kmem_cache ||
>> mc->gfp_zero)))
>> +            return -EIO;
>> +
>>           mc->objects = kvmalloc_array(capacity, sizeof(void *), gfp);
>>           if (!mc->objects)
>>               return -ENOMEM;
>
>