Linux-HyperV Archive on lore.kernel.org
 help / color / Atom feed
From: Jon Doron <arilou@gmail.com>
To: kvm@vger.kernel.org, linux-hyperv@vger.kernel.org
Cc: vkuznets@redhat.com, Jon Doron <arilou@gmail.com>
Subject: [PATCH v11 1/7] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit
Date: Fri, 24 Apr 2020 14:37:40 +0300
Message-ID: <20200424113746.3473563-2-arilou@gmail.com> (raw)
In-Reply-To: <20200424113746.3473563-1-arilou@gmail.com>

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(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index efbbe570aa9b..750d005a75bc 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5067,9 +5067,11 @@ 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 428c7dde6b4b..9cdc5356f542 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;
-- 
2.24.1


  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 ` Jon Doron [this message]
2020-05-13  8:42   ` [PATCH v11 1/7] x86/kvm/hyper-v: Explicitly align hcall param for kvm_hyperv_exit Roman Kagan
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

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=20200424113746.3473563-2-arilou@gmail.com \
    --to=arilou@gmail.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=vkuznets@redhat.com \
    /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

Linux-HyperV Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-hyperv/0 linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ https://lore.kernel.org/linux-hyperv \
		linux-hyperv@vger.kernel.org
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-hyperv


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git