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From: Roman Kagan <rvkagan@yandex-team.ru>
To: Jon Doron <arilou@gmail.com>
Cc: kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, vkuznets@redhat.com
Subject: Re: [PATCH v11 1/7] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit
Date: Wed, 13 May 2020 11:42:44 +0300
Message-ID: <20200513084244.GA29650@rvkaganb.lan> (raw)
In-Reply-To: <20200424113746.3473563-2-arilou@gmail.com>

On Fri, Apr 24, 2020 at 02:37:40PM +0300, Jon Doron wrote:
> The problem the patch is trying to address is the fact that 'struct
> kvm_hyperv_exit' has different layout on when compiling in 32 and 64 bit
> modes.
> 
> In 64-bit mode the default alignment boundary is 64 bits thus
> forcing extra gaps after 'type' and 'msr' but in 32-bit mode the
> boundary is at 32 bits thus no extra gaps.
> 
> This is an issue as even when the kernel is 64 bit, the userspace using
> the interface can be both 32 and 64 bit but the same 32 bit userspace has
> to work with 32 bit kernel.
> 
> The issue is fixed by forcing the 64 bit layout, this leads to ABI
> change for 32 bit builds and while we are obviously breaking '32 bit
> userspace with 32 bit kernel' case, we're fixing the '32 bit userspace
> with 64 bit kernel' one.
> 
> As the interface has no (known) users and 32 bit KVM is rather baroque
> nowadays, this seems like a reasonable decision.
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Jon Doron <arilou@gmail.com>
> ---
>  Documentation/virt/kvm/api.rst | 2 ++
>  include/uapi/linux/kvm.h       | 2 ++
>  2 files changed, 4 insertions(+)

Reviewed-by: Roman Kagan <rvkagan@yandex-team.ru>

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-24 11:37 [PATCH v11 0/7] x86/kvm/hyper-v: add support for synthetic debugger Jon Doron
2020-04-24 11:37 ` [PATCH v11 1/7] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit Jon Doron
2020-05-13  8:42   ` Roman Kagan [this message]
2020-04-24 11:37 ` [PATCH v11 2/7] x86/kvm/hyper-v: Simplify addition for custom cpuid leafs Jon Doron
2020-05-13  9:24   ` Roman Kagan
2020-05-13 12:49     ` Jon Doron
2020-05-29 11:13       ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 3/7] x86/hyper-v: Add synthetic debugger definitions Jon Doron
2020-04-24 11:37 ` [PATCH v11 4/7] x86/kvm/hyper-v: Add support for synthetic debugger capability Jon Doron
2020-05-29 10:46   ` Paolo Bonzini
2020-05-29 12:08     ` Vitaly Kuznetsov
2020-05-29 12:17       ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 5/7] x86/kvm/hyper-v: enable hypercalls without hypercall page with syndbg Jon Doron
2020-05-13  9:57   ` Roman Kagan
2020-05-13 12:37     ` Jon Doron
2020-05-29 10:48   ` Paolo Bonzini
2020-04-24 11:37 ` [PATCH v11 6/7] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls Jon Doron
2020-05-12 15:33   ` Roman Kagan
2020-05-13 12:39     ` Jon Doron
2020-04-24 11:37 ` [PATCH v11 7/7] KVM: selftests: update hyperv_cpuid with SynDBG tests Jon Doron
2020-05-07  3:01 ` [PATCH v11 0/7] x86/kvm/hyper-v: add support for synthetic debugger Jon Doron
2020-05-07  7:57   ` Paolo Bonzini

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