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Message-ID: <20230719075440.m3h653frqggaiusc@yy-desk-7060>
Date: Wed, 19 Jul 2023 15:54:40 +0800
From: Yuan Yao <yuan.yao@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
Huacai Chen <chenhuacai@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
Anup Patel <anup@...infault.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>, kvm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
Chao Peng <chao.p.peng@...ux.intel.com>,
Fuad Tabba <tabba@...gle.com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Yu Zhang <yu.c.zhang@...ux.intel.com>,
Vishal Annapurve <vannapurve@...gle.com>,
Ackerley Tng <ackerleytng@...gle.com>,
Maciej Szmigiero <mail@...iej.szmigiero.name>,
Vlastimil Babka <vbabka@...e.cz>,
David Hildenbrand <david@...hat.com>,
Quentin Perret <qperret@...gle.com>,
Michael Roth <michael.roth@....com>,
Wang <wei.w.wang@...el.com>,
Liam Merwick <liam.merwick@...cle.com>,
Isaku Yamahata <isaku.yamahata@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 07/29] KVM: Add KVM_EXIT_MEMORY_FAULT exit
On Tue, Jul 18, 2023 at 04:44:50PM -0700, Sean Christopherson wrote:
> From: Chao Peng <chao.p.peng@...ux.intel.com>
>
> This new KVM exit allows userspace to handle memory-related errors. It
> indicates an error happens in KVM at guest memory range [gpa, gpa+size).
> The flags includes additional information for userspace to handle the
> error. Currently bit 0 is defined as 'private memory' where '1'
> indicates error happens due to private memory access and '0' indicates
> error happens due to shared memory access.
Now it's bit 3:
#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
I remember some other attributes were introduced in v10 yet:
#define KVM_MEMORY_ATTRIBUTE_READ (1ULL << 0)
#define KVM_MEMORY_ATTRIBUTE_WRITE (1ULL << 1)
#define KVM_MEMORY_ATTRIBUTE_EXECUTE (1ULL << 2)
#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
So KVM_MEMORY_EXIT_FLAG_PRIVATE changed to bit 3 due to above things,
or other reason ? (Sorry I didn't follow v10 too much before).
>
> When private memory is enabled, this new exit will be used for KVM to
> exit to userspace for shared <-> private memory conversion in memory
> encryption usage. In such usage, typically there are two kind of memory
> conversions:
> - explicit conversion: happens when guest explicitly calls into KVM
> to map a range (as private or shared), KVM then exits to userspace
> to perform the map/unmap operations.
> - implicit conversion: happens in KVM page fault handler where KVM
> exits to userspace for an implicit conversion when the page is in a
> different state than requested (private or shared).
>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Co-developed-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
> Signed-off-by: Yu Zhang <yu.c.zhang@...ux.intel.com>
> Signed-off-by: Chao Peng <chao.p.peng@...ux.intel.com>
> Reviewed-by: Fuad Tabba <tabba@...gle.com>
> Tested-by: Fuad Tabba <tabba@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++
> include/uapi/linux/kvm.h | 8 ++++++++
> 2 files changed, 30 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index c0ddd3035462..34d4ce66e0c8 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6700,6 +6700,28 @@ array field represents return values. The userspace should update the return
> values of SBI call before resuming the VCPU. For more details on RISC-V SBI
> spec refer, https://github.com/riscv/riscv-sbi-doc.
>
> +::
> +
> + /* KVM_EXIT_MEMORY_FAULT */
> + struct {
> + #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
> + __u64 flags;
> + __u64 gpa;
> + __u64 size;
> + } memory;
> +
> +If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has
> +encountered a memory error which is not handled by KVM kernel module and
> +userspace may choose to handle it. The 'flags' field indicates the memory
> +properties of the exit.
> +
> + - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by
> + private memory access when the bit is set. Otherwise the memory error is
> + caused by shared memory access when the bit is clear.
> +
> +'gpa' and 'size' indicate the memory range the error occurs at. The userspace
> +may handle the error and return to KVM to retry the previous memory access.
> +
> ::
>
> /* KVM_EXIT_NOTIFY */
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4d4b3de8ac55..6c6ed214b6ac 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -274,6 +274,7 @@ struct kvm_xen_exit {
> #define KVM_EXIT_RISCV_SBI 35
> #define KVM_EXIT_RISCV_CSR 36
> #define KVM_EXIT_NOTIFY 37
> +#define KVM_EXIT_MEMORY_FAULT 38
>
> /* For KVM_EXIT_INTERNAL_ERROR */
> /* Emulate instruction failed. */
> @@ -520,6 +521,13 @@ struct kvm_run {
> #define KVM_NOTIFY_CONTEXT_INVALID (1 << 0)
> __u32 flags;
> } notify;
> + /* KVM_EXIT_MEMORY_FAULT */
> + struct {
> +#define KVM_MEMORY_EXIT_FLAG_PRIVATE (1ULL << 3)
> + __u64 flags;
> + __u64 gpa;
> + __u64 size;
> + } memory;
> /* Fix the size of the union. */
> char padding[256];
> };
> --
> 2.41.0.255.g8b1d071c50-goog
>
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