From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: "H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@amacapital.net>
Cc: David Vrabel <david.vrabel@citrix.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
Date: Tue, 17 Nov 2015 09:40:23 -0500 [thread overview]
Message-ID: <564B3C57.5000002__24847.1118895852$1447771334$gmane$org@oracle.com> (raw)
In-Reply-To: <564A50C3.1000200@zytor.com>
On 11/16/2015 04:55 PM, H. Peter Anvin wrote:
> On 11/16/15 12:22, Borislav Petkov wrote:
>> Huh, so what's wrong with a jump:
>>
>> jmp 1f
>> swapgs
>> 1:
>>
> What is the point of that jump?
>
>>> If it would make you feel better, it could be X86_BUG_XENPV :-p
>> That doesn't matter - I just don't want to open the flood gates on
>> pseudo feature bits.
>>
>> hpa, what do you think?
> Pseudo feature bits are fine, we already have plenty of them. They make
> sense as they let us reuse a lot of infrastructure.
So how about something like this? And then I think we can remove
usergs_sysret32 and irq_enable_sysexit pv ops completely as noone will
use them (lguest doesn't set them)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 3eb572e..c43df7b 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -308,7 +308,8 @@ sysenter_past_esp:
movl %esp, %eax
call do_fast_syscall_32
- testl %eax, %eax
+ /* PV guests always use IRET path */
+ ALTERNATIVE "testl %eax, %eax", "jmp .Lsyscall_32_done",
X86_FEATURE_PV
jz .Lsyscall_32_done
/* Opportunistic SYSEXIT */
diff --git a/arch/x86/entry/entry_64_compat.S
b/arch/x86/entry/entry_64_compat.S
index c320183..2d1bc82 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -121,7 +121,7 @@ sysenter_flags_fixed:
movq %rsp, %rdi
call do_fast_syscall_32
- testl %eax, %eax
+ ALTERNATIVE "testl %eax, %eax", "jmp .Lsyscall_32_done",
X86_FEATURE_PV
jz .Lsyscall_32_done
jmp sysret32_from_system_call
@@ -200,7 +200,8 @@ ENTRY(entry_SYSCALL_compat)
movq %rsp, %rdi
call do_fast_syscall_32
- testl %eax, %eax
+ /* PV guests always use IRET path */
+ ALTERNATIVE "testl %eax, %eax", "jmp .Lsyscall_32_done",
X86_FEATURE_PV
jz .Lsyscall_32_done
/* Opportunistic SYSRET */
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index e4f8010..723327b 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -216,6 +216,7 @@
#define X86_FEATURE_PAUSEFILTER ( 8*32+13) /* AMD filtered pause
intercept */
#define X86_FEATURE_PFTHRESHOLD ( 8*32+14) /* AMD pause filter
threshold */
#define X86_FEATURE_VMMCALL ( 8*32+15) /* Prefer vmmcall to vmcall */
+#define X86_FEATURE_PV ( 8*32+16) /* Paravirtual guest */
/* Intel-defined CPU features, CPUID level 0x00000007:0 (ebx), word 9 */
next prev parent reply other threads:[~2015-11-17 14:40 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-13 23:18 [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Boris Ostrovsky
2015-11-13 23:26 ` Andy Lutomirski
2015-11-14 1:23 ` Boris Ostrovsky
2015-11-14 1:23 ` Boris Ostrovsky
2015-11-15 18:02 ` Andy Lutomirski
2015-11-15 18:02 ` Andy Lutomirski
2015-11-16 16:25 ` Boris Ostrovsky
2015-11-16 16:25 ` Boris Ostrovsky
2015-11-16 19:03 ` Andy Lutomirski
2015-11-16 19:59 ` Borislav Petkov
2015-11-16 20:11 ` Andy Lutomirski
2015-11-16 20:11 ` Andy Lutomirski
2015-11-16 20:22 ` Borislav Petkov
2015-11-16 20:22 ` Borislav Petkov
2015-11-16 20:48 ` Boris Ostrovsky
2015-11-16 20:50 ` Andy Lutomirski
2015-11-16 21:00 ` Borislav Petkov
2015-11-16 21:00 ` Borislav Petkov
2015-11-16 21:03 ` Konrad Rzeszutek Wilk
2015-11-16 21:04 ` Andy Lutomirski
2015-11-17 10:53 ` Joao Martins
2015-11-17 10:53 ` Joao Martins
2015-11-16 21:04 ` Andy Lutomirski
2015-11-16 20:50 ` Andy Lutomirski
2015-11-16 20:48 ` Boris Ostrovsky
2015-11-16 21:55 ` H. Peter Anvin
2015-11-16 21:55 ` H. Peter Anvin
2015-11-17 14:40 ` Boris Ostrovsky [this message]
2015-11-17 14:40 ` Boris Ostrovsky
2015-11-17 18:49 ` Andy Lutomirski
2015-11-17 19:12 ` Andrew Cooper
2015-11-17 19:12 ` [Xen-devel] " Andrew Cooper
2015-11-17 19:16 ` Andy Lutomirski
2015-11-17 19:21 ` Borislav Petkov
2015-11-17 19:21 ` [Xen-devel] " Borislav Petkov
2015-11-17 19:29 ` Andrew Cooper
2015-11-17 19:36 ` Andy Lutomirski
2015-11-17 19:36 ` Andy Lutomirski
2015-11-17 19:29 ` Andrew Cooper
2015-11-17 19:37 ` [Xen-devel] " Boris Ostrovsky
2015-11-17 19:38 ` Boris Ostrovsky
2015-11-17 19:38 ` [Xen-devel] " Boris Ostrovsky
2015-11-17 19:37 ` Boris Ostrovsky
2015-11-17 19:16 ` Andy Lutomirski
2015-11-17 18:49 ` Andy Lutomirski
2015-11-16 19:59 ` Borislav Petkov
2015-11-16 20:31 ` Boris Ostrovsky
2015-11-16 20:31 ` Boris Ostrovsky
2015-11-16 19:03 ` Andy Lutomirski
2015-11-13 23:26 ` Andy Lutomirski
2015-11-13 23:18 Boris Ostrovsky
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='564B3C57.5000002__24847.1118895852$1447771334$gmane$org@oracle.com' \
--to=boris.ostrovsky@oracle.com \
--cc=bp@alien8.de \
--cc=david.vrabel@citrix.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=xen-devel@lists.xen.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.