From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Jon Doron <arilou@gmail.com>
Cc: kvm@vger.kernel.org, linux-hyperv@vger.kernel.org
Subject: Re: [PATCH v9 1/6] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit
Date: Mon, 23 Mar 2020 10:53:19 +0100 [thread overview]
Message-ID: <87zhc79z3k.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200320172839.1144395-2-arilou@gmail.com>
Jon Doron <arilou@gmail.com> writes:
> 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.
>
> 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(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index ebd383fba939..4872c47bbcff 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5025,9 +5025,11 @@ EOI was received.
> #define KVM_EXIT_HYPERV_SYNIC 1
> #define KVM_EXIT_HYPERV_HCALL 2
> __u32 type;
> + __u32 pad1;
> union {
> struct {
> __u32 msr;
> + __u32 pad2;
> __u64 control;
> __u64 evt_page;
> __u64 msg_page;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4b95f9a31a2f..7ee0ddc4c457 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -189,9 +189,11 @@ struct kvm_hyperv_exit {
> #define KVM_EXIT_HYPERV_SYNIC 1
> #define KVM_EXIT_HYPERV_HCALL 2
> __u32 type;
> + __u32 pad1;
> union {
> struct {
> __u32 msr;
> + __u32 pad2;
> __u64 control;
> __u64 evt_page;
> __u64 msg_page;
Already said that on v8 but the tag got lost,
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
next prev parent reply other threads:[~2020-03-23 9:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 17:28 [PATCH v9 0/6] x86/kvm/hyper-v: add support for synthetic debugger Jon Doron
2020-03-20 17:28 ` [PATCH v9 1/6] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit Jon Doron
2020-03-23 9:53 ` Vitaly Kuznetsov [this message]
2020-03-20 17:28 ` [PATCH v9 2/6] x86/kvm/hyper-v: Simplify addition for custom cpuid leafs Jon Doron
2020-03-23 10:16 ` Vitaly Kuznetsov
2020-03-20 17:28 ` [PATCH v9 3/6] x86/hyper-v: Add synthetic debugger definitions Jon Doron
2020-03-23 10:17 ` Vitaly Kuznetsov
2020-03-20 17:28 ` [PATCH v9 4/6] x86/kvm/hyper-v: Add support for synthetic debugger capability Jon Doron
2020-03-23 10:36 ` Vitaly Kuznetsov
2020-03-20 17:28 ` [PATCH v9 5/6] x86/kvm/hyper-v: enable hypercalls without hypercall page with syndbg Jon Doron
2020-03-20 17:28 ` [PATCH v9 6/6] x86/kvm/hyper-v: Add support for synthetic debugger via hypercalls Jon Doron
2020-03-23 9:51 ` [PATCH v9 7/6] KVM: selftests: update hyperv_cpuid with SynDBG tests Vitaly Kuznetsov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87zhc79z3k.fsf@vitty.brq.redhat.com \
--to=vkuznets@redhat.com \
--cc=arilou@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-hyperv@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).