* [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
@ 2019-02-06 11:52 Kirill A. Shutemov
2019-02-06 15:21 ` Borislav Petkov
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Kirill A. Shutemov @ 2019-02-06 11:52 UTC (permalink / raw)
To: tglx, mingo, bp, hpa, dave.hansen
Cc: x86, linux-kernel, Kirill A. Shutemov, Kyle D Pelton, Wei Huang
RDMSR in the trampoline code overrides EDX, but we use the register to
indicate if 5-level paging has to enabled. It leads to failure to boot
on a 5-level paging machine.
Preserve EDX on the stack while we are dealing with EFER.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: b677dfae5aa1 ("x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode")
Reported-by: Kyle D Pelton <kyle.d.pelton@intel.com>
Cc: Wei Huang <wei@redhat.com>
---
arch/x86/boot/compressed/head_64.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index f105ae8651c9..f62e347862cc 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -602,10 +602,12 @@ ENTRY(trampoline_32bit_src)
3:
/* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
pushl %ecx
+ pushl %edx
movl $MSR_EFER, %ecx
rdmsr
btsl $_EFER_LME, %eax
wrmsr
+ popl %edx
popl %ecx
/* Enable PAE and LA57 (if required) paging modes */
--
2.20.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
2019-02-06 11:52 [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting Kirill A. Shutemov
@ 2019-02-06 15:21 ` Borislav Petkov
2019-02-06 15:47 ` Kirill A. Shutemov
2019-02-06 18:04 ` [tip:x86/urgent] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting tip-bot for Kirill A. Shutemov
2019-02-06 19:50 ` [PATCH] " Wei Huang
2 siblings, 1 reply; 7+ messages in thread
From: Borislav Petkov @ 2019-02-06 15:21 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: tglx, mingo, hpa, dave.hansen, x86, linux-kernel, Kyle D Pelton,
Wei Huang
On Wed, Feb 06, 2019 at 02:52:53PM +0300, Kirill A. Shutemov wrote:
> RDMSR in the trampoline code overrides EDX, but we use the register to
> indicate if 5-level paging has to enabled. It leads to failure to boot
> on a 5-level paging machine.
>
> Preserve EDX on the stack while we are dealing with EFER.
Comment says:
* Non zero RDX on return means we need to enable 5-level paging.
Is that per-chance refering to struct paging_config which
paging_prepare() returns and on that return rdx contains
paging_config.l5_required which is 1 when 5 level is to be enabled?
If so, is that written somewhere explicitly? Because it is not
immediately clear at least to me why that RDX is live...
Thx.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
2019-02-06 15:21 ` Borislav Petkov
@ 2019-02-06 15:47 ` Kirill A. Shutemov
2019-02-06 18:11 ` Borislav Petkov
2019-02-06 18:13 ` [tip:x86/cleanups] x86/boot/compressed/64: Explain paging_prepare()'s return value tip-bot for Kirill A. Shutemov
0 siblings, 2 replies; 7+ messages in thread
From: Kirill A. Shutemov @ 2019-02-06 15:47 UTC (permalink / raw)
To: Borislav Petkov
Cc: tglx, mingo, hpa, dave.hansen, x86, linux-kernel, Kyle D Pelton,
Wei Huang
On Wed, Feb 06, 2019 at 03:21:41PM +0000, Borislav Petkov wrote:
> On Wed, Feb 06, 2019 at 02:52:53PM +0300, Kirill A. Shutemov wrote:
> > RDMSR in the trampoline code overrides EDX, but we use the register to
> > indicate if 5-level paging has to enabled. It leads to failure to boot
> > on a 5-level paging machine.
> >
> > Preserve EDX on the stack while we are dealing with EFER.
>
> Comment says:
>
> * Non zero RDX on return means we need to enable 5-level paging.
>
> Is that per-chance refering to struct paging_config which
> paging_prepare() returns and on that return rdx contains
> paging_config.l5_required which is 1 when 5 level is to be enabled?
Yes.
> If so, is that written somewhere explicitly? Because it is not
> immediately clear at least to me why that RDX is live...
What about this:
From d43b9d157c574baf782f6d9982fe6f2c1f918c0e Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date: Wed, 6 Feb 2019 18:29:08 +0300
Subject: [PATCH] x86/boot/compressed/64: Fix confusing comment for
paging_config()
paging_prepare() returns two-quadword structure which lands
into RDX:RAX:
- Address of the trampoline is returned in RAX.
- Non zero RDX means trampoline needs to enable 5-level paging.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/boot/compressed/head_64.S | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index f62e347862cc..87509a3f00f4 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -358,8 +358,11 @@ ENTRY(startup_64)
* paging_prepare() sets up the trampoline and checks if we need to
* enable 5-level paging.
*
- * Address of the trampoline is returned in RAX.
- * Non zero RDX on return means we need to enable 5-level paging.
+ * paging_prepare() returns two-quadword structure which lands
+ * into RDX:RAX:
+ * - Address of the trampoline is returned in RAX.
+ * - Non zero RDX means trampoline needs to enable 5-level
+ * paging.
*
* RSI holds real mode data and needs to be preserved across
* this function call.
@@ -565,7 +568,7 @@ adjust_got:
*
* RDI contains the return address (might be above 4G).
* ECX contains the base address of the trampoline memory.
- * Non zero RDX on return means we need to enable 5-level paging.
+ * Non zero RDX means trampoline needs to enable 5-level paging.
*/
ENTRY(trampoline_32bit_src)
/* Set up data and stack segments */
--
Kirill A. Shutemov
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [tip:x86/urgent] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
2019-02-06 11:52 [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting Kirill A. Shutemov
2019-02-06 15:21 ` Borislav Petkov
@ 2019-02-06 18:04 ` tip-bot for Kirill A. Shutemov
2019-02-06 19:50 ` [PATCH] " Wei Huang
2 siblings, 0 replies; 7+ messages in thread
From: tip-bot for Kirill A. Shutemov @ 2019-02-06 18:04 UTC (permalink / raw)
To: linux-tip-commits
Cc: kyle.d.pelton, mingo, x86, hpa, linux-kernel, bp, wei, mingo,
tglx, kirill.shutemov
Commit-ID: 45b13b424faafb81c8c44541f093a682fdabdefc
Gitweb: https://git.kernel.org/tip/45b13b424faafb81c8c44541f093a682fdabdefc
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate: Wed, 6 Feb 2019 14:52:53 +0300
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Wed, 6 Feb 2019 18:56:18 +0100
x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
RDMSR in the trampoline code overwrites EDX but that register is used
to indicate whether 5-level paging has to be enabled and if clobbered,
leads to failure to boot on a 5-level paging machine.
Preserve EDX on the stack while we are dealing with EFER.
Fixes: b677dfae5aa1 ("x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode")
Reported-by: Kyle D Pelton <kyle.d.pelton@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: dave.hansen@linux.intel.com
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Huang <wei@redhat.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190206115253.1907-1-kirill.shutemov@linux.intel.com
---
arch/x86/boot/compressed/head_64.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index f105ae8651c9..f62e347862cc 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -602,10 +602,12 @@ ENTRY(trampoline_32bit_src)
3:
/* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
pushl %ecx
+ pushl %edx
movl $MSR_EFER, %ecx
rdmsr
btsl $_EFER_LME, %eax
wrmsr
+ popl %edx
popl %ecx
/* Enable PAE and LA57 (if required) paging modes */
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
2019-02-06 15:47 ` Kirill A. Shutemov
@ 2019-02-06 18:11 ` Borislav Petkov
2019-02-06 18:13 ` [tip:x86/cleanups] x86/boot/compressed/64: Explain paging_prepare()'s return value tip-bot for Kirill A. Shutemov
1 sibling, 0 replies; 7+ messages in thread
From: Borislav Petkov @ 2019-02-06 18:11 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: tglx, mingo, hpa, dave.hansen, x86, linux-kernel, Kyle D Pelton,
Wei Huang
On Wed, Feb 06, 2019 at 06:47:57PM +0300, Kirill A. Shutemov wrote:
> What about this:
Yap, thanks!
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [tip:x86/cleanups] x86/boot/compressed/64: Explain paging_prepare()'s return value
2019-02-06 15:47 ` Kirill A. Shutemov
2019-02-06 18:11 ` Borislav Petkov
@ 2019-02-06 18:13 ` tip-bot for Kirill A. Shutemov
1 sibling, 0 replies; 7+ messages in thread
From: tip-bot for Kirill A. Shutemov @ 2019-02-06 18:13 UTC (permalink / raw)
To: linux-tip-commits
Cc: wei, bp, mingo, kirill.shutemov, mingo, hpa, kyle.d.pelton,
linux-kernel, tglx, x86
Commit-ID: 82434d23f36de42f70925f70d645ed3b1394361b
Gitweb: https://git.kernel.org/tip/82434d23f36de42f70925f70d645ed3b1394361b
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate: Wed, 6 Feb 2019 18:29:08 +0300
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Wed, 6 Feb 2019 19:08:34 +0100
x86/boot/compressed/64: Explain paging_prepare()'s return value
paging_prepare() returns a two-quadword structure which lands
into RDX:RAX:
- Address of the trampoline is returned in RAX.
- Non zero RDX means trampoline needs to enable 5-level paging.
Document that explicitly.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: dave.hansen@linux.intel.com
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kyle D Pelton <kyle.d.pelton@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Huang <wei@redhat.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190206154756.matwldebbxkmlnae@black.fi.intel.com
---
arch/x86/boot/compressed/head_64.S | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index b27b338d2f6d..73b9d7e91a9c 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -358,8 +358,11 @@ ENTRY(startup_64)
* paging_prepare() sets up the trampoline and checks if we need to
* enable 5-level paging.
*
- * Address of the trampoline is returned in RAX.
- * Non zero RDX on return means we need to enable 5-level paging.
+ * paging_prepare() returns a two-quadword structure which lands
+ * into RDX:RAX:
+ * - Address of the trampoline is returned in RAX.
+ * - Non zero RDX means trampoline needs to enable 5-level
+ * paging.
*
* RSI holds real mode data and needs to be preserved across
* this function call.
@@ -565,7 +568,7 @@ adjust_got:
*
* RDI contains the return address (might be above 4G).
* ECX contains the base address of the trampoline memory.
- * Non zero RDX on return means we need to enable 5-level paging.
+ * Non zero RDX means trampoline needs to enable 5-level paging.
*/
ENTRY(trampoline_32bit_src)
/* Set up data and stack segments */
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting
2019-02-06 11:52 [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting Kirill A. Shutemov
2019-02-06 15:21 ` Borislav Petkov
2019-02-06 18:04 ` [tip:x86/urgent] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting tip-bot for Kirill A. Shutemov
@ 2019-02-06 19:50 ` Wei Huang
2 siblings, 0 replies; 7+ messages in thread
From: Wei Huang @ 2019-02-06 19:50 UTC (permalink / raw)
To: Kirill A. Shutemov, tglx, mingo, bp, hpa, dave.hansen
Cc: x86, linux-kernel, Kyle D Pelton
On 2/6/19 5:52 AM, Kirill A. Shutemov wrote:
> RDMSR in the trampoline code overrides EDX, but we use the register to
> indicate if 5-level paging has to enabled. It leads to failure to boot
> on a 5-level paging machine.
>
> Preserve EDX on the stack while we are dealing with EFER.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: b677dfae5aa1 ("x86/boot/compressed/64: Set EFER.LME=1 in 32-bit trampoline before returning to long mode")
> Reported-by: Kyle D Pelton <kyle.d.pelton@intel.com>
> Cc: Wei Huang <wei@redhat.com>
> ---
> arch/x86/boot/compressed/head_64.S | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index f105ae8651c9..f62e347862cc 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -602,10 +602,12 @@ ENTRY(trampoline_32bit_src)
> 3:
> /* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
> pushl %ecx
> + pushl %edx
> movl $MSR_EFER, %ecx
> rdmsr
> btsl $_EFER_LME, %eax
> wrmsr
> + popl %edx
> popl %ecx
>
> /* Enable PAE and LA57 (if required) paging modes */
>
Oops, rdmsr indeed corrupts EDX.
Acked-by: Wei Huang <wei@redhat.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2019-02-06 19:50 UTC | newest]
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2019-02-06 11:52 [PATCH] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting Kirill A. Shutemov
2019-02-06 15:21 ` Borislav Petkov
2019-02-06 15:47 ` Kirill A. Shutemov
2019-02-06 18:11 ` Borislav Petkov
2019-02-06 18:13 ` [tip:x86/cleanups] x86/boot/compressed/64: Explain paging_prepare()'s return value tip-bot for Kirill A. Shutemov
2019-02-06 18:04 ` [tip:x86/urgent] x86/boot/compressed/64: Do not corrupt EDX on EFER.LME=1 setting tip-bot for Kirill A. Shutemov
2019-02-06 19:50 ` [PATCH] " Wei Huang
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