All of lore.kernel.org
 help / color / mirror / Atom feed
From: Baoquan He <bhe@redhat.com>
To: Borislav Petkov <bp@suse.de>
Cc: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
	"Singh, Brijesh" <brijesh.singh@amd.com>,
	Kairui Song <kasong@redhat.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"dyoung@redhat.com" <dyoung@redhat.com>
Subject: Re: [PATCH] x86/boot: Fix kexec booting failure after SEV early boot support
Date: Wed, 26 Sep 2018 15:32:52 +0800	[thread overview]
Message-ID: <20180926073252.GC2555@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20180925172608.GB15464@zn.tnic>

On 09/25/18 at 07:26pm, Borislav Petkov wrote:
> IINM, the problem can be addressed in a simpler way by getting rid of
> enc_bit and thus getting rid of the need to do relative addressing of
> anything and simply doing the whole dance of figuring out the C-bit each
> time. It probably wouldn't be even measurable...

Couldn't agree more.

Obviously enc_bit is redundent here. We only check eax each time,
removing it can fix the RIP-relative addressing issue in kexec.

diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index eaa843a52907..0b60eb867d25 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -27,19 +27,6 @@ ENTRY(get_sev_encryption_bit)
 	push	%edx
 	push	%edi
 
-	/*
-	 * RIP-relative addressing is needed to access the encryption bit
-	 * variable. Since we are running in 32-bit mode we need this call/pop
-	 * sequence to get the proper relative addressing.
-	 */
-	call	1f
-1:	popl	%edi
-	subl	$1b, %edi
-
-	movl	enc_bit(%edi), %eax
-	cmpl	$0, %eax
-	jge	.Lsev_exit
-
 	/* Check if running under a hypervisor */
 	movl	$1, %eax
 	cpuid
@@ -69,12 +56,10 @@ ENTRY(get_sev_encryption_bit)
 
 	movl	%ebx, %eax
 	andl	$0x3f, %eax		/* Return the encryption bit location */
-	movl	%eax, enc_bit(%edi)
 	jmp	.Lsev_exit
 
 .Lno_sev:
 	xor	%eax, %eax
-	movl	%eax, enc_bit(%edi)
 
 .Lsev_exit:
 	pop	%edi
@@ -113,9 +98,6 @@ ENTRY(set_sev_encryption_mask)
 ENDPROC(set_sev_encryption_mask)
 
 	.data
-enc_bit:
-	.int	0xffffffff
-
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 	.balign	8
 GLOBAL(sme_me_mask)

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: Baoquan He <bhe@redhat.com>
To: Borislav Petkov <bp@suse.de>
Cc: "Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
	Kairui Song <kasong@redhat.com>,
	"Singh, Brijesh" <brijesh.singh@amd.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"hpa@zytor.com" <hpa@zytor.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"dyoung@redhat.com" <dyoung@redhat.com>
Subject: Re: [PATCH] x86/boot: Fix kexec booting failure after SEV early boot support
Date: Wed, 26 Sep 2018 15:32:52 +0800	[thread overview]
Message-ID: <20180926073252.GC2555@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20180925172608.GB15464@zn.tnic>

On 09/25/18 at 07:26pm, Borislav Petkov wrote:
> IINM, the problem can be addressed in a simpler way by getting rid of
> enc_bit and thus getting rid of the need to do relative addressing of
> anything and simply doing the whole dance of figuring out the C-bit each
> time. It probably wouldn't be even measurable...

Couldn't agree more.

Obviously enc_bit is redundent here. We only check eax each time,
removing it can fix the RIP-relative addressing issue in kexec.

diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index eaa843a52907..0b60eb867d25 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -27,19 +27,6 @@ ENTRY(get_sev_encryption_bit)
 	push	%edx
 	push	%edi
 
-	/*
-	 * RIP-relative addressing is needed to access the encryption bit
-	 * variable. Since we are running in 32-bit mode we need this call/pop
-	 * sequence to get the proper relative addressing.
-	 */
-	call	1f
-1:	popl	%edi
-	subl	$1b, %edi
-
-	movl	enc_bit(%edi), %eax
-	cmpl	$0, %eax
-	jge	.Lsev_exit
-
 	/* Check if running under a hypervisor */
 	movl	$1, %eax
 	cpuid
@@ -69,12 +56,10 @@ ENTRY(get_sev_encryption_bit)
 
 	movl	%ebx, %eax
 	andl	$0x3f, %eax		/* Return the encryption bit location */
-	movl	%eax, enc_bit(%edi)
 	jmp	.Lsev_exit
 
 .Lno_sev:
 	xor	%eax, %eax
-	movl	%eax, enc_bit(%edi)
 
 .Lsev_exit:
 	pop	%edi
@@ -113,9 +98,6 @@ ENTRY(set_sev_encryption_mask)
 ENDPROC(set_sev_encryption_mask)
 
 	.data
-enc_bit:
-	.int	0xffffffff
-
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 	.balign	8
 GLOBAL(sme_me_mask)

  reply	other threads:[~2018-09-26  7:33 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-25 11:10 [PATCH] x86/boot: Fix kexec booting failure after SEV early boot support Kairui Song
2018-09-25 11:10 ` Kairui Song
2018-09-25 14:33 ` Lendacky, Thomas
2018-09-25 14:33   ` Lendacky, Thomas
2018-09-25 17:26   ` Borislav Petkov
2018-09-25 17:26     ` Borislav Petkov
2018-09-26  7:32     ` Baoquan He [this message]
2018-09-26  7:32       ` Baoquan He
2018-09-26 10:52       ` Kairui Song
2018-09-26 10:52         ` Kairui Song
2018-09-26 11:22       ` Baoquan He
2018-09-26 11:22         ` Baoquan He
2018-09-26 13:01         ` Lendacky, Thomas
2018-09-26 13:01           ` Lendacky, Thomas
2018-09-26 13:18           ` Borislav Petkov
2018-09-26 13:18             ` Borislav Petkov
2018-09-26 13:21           ` Baoquan He
2018-09-26 13:21             ` Baoquan He
  -- strict thread matches above, loose matches on Subject: below --
2018-09-27 12:38 Kairui Song
2018-09-27 12:38 ` Kairui Song
2018-09-27 13:16 ` Lendacky, Thomas
2018-09-27 13:16   ` Lendacky, Thomas

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=20180926073252.GC2555@MiWiFi-R3L-srv \
    --to=bhe@redhat.com \
    --cc=Thomas.Lendacky@amd.com \
    --cc=bp@suse.de \
    --cc=brijesh.singh@amd.com \
    --cc=dyoung@redhat.com \
    --cc=hpa@zytor.com \
    --cc=kasong@redhat.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@linutronix.de \
    --cc=x86@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 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.