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* [kvm-unit-tests PATCH] x86: Fix breakage of fw_cfg for 32-bit unit tests
@ 2019-08-22 23:50 Sean Christopherson
  2019-08-22 23:55 ` Nadav Amit
  0 siblings, 1 reply; 3+ messages in thread
From: Sean Christopherson @ 2019-08-22 23:50 UTC (permalink / raw)
  To: Paolo Bonzini, Radim Krčmář; +Cc: kvm, Nadav Amit

Ensure the fw_cfg overrides are parsed prior consuming any of said
overrides.  fwcfg_get_u() treats zero as a valid overide value, which
is slightly problematic since the overrides are in the .bss and thus
initialized to zero.

Add a limit check when indexing fw_override so that future code doesn't
spontaneously explode.

Cc: Nadav Amit <nadav.amit@gmail.com>
Fixes: 03b1e4570f967 ("x86: Support environments without test-devices")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 lib/x86/fwcfg.c | 10 ++++++++--
 lib/x86/fwcfg.h |  2 --
 x86/cstart64.S  |  2 --
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/x86/fwcfg.c b/lib/x86/fwcfg.c
index d8d797f..06ef62c 100644
--- a/lib/x86/fwcfg.c
+++ b/lib/x86/fwcfg.c
@@ -5,10 +5,11 @@
 static struct spinlock lock;
 
 static long fw_override[FW_CFG_MAX_ENTRY];
+static bool fw_override_done;
 
 bool no_test_device;
 
-void read_cfg_override(void)
+static void read_cfg_override(void)
 {
 	const char *str;
 	int i;
@@ -26,6 +27,8 @@ void read_cfg_override(void)
 
 	if ((str = getenv("TEST_DEVICE")))
 		no_test_device = !atol(str);
+
+    fw_override_done = true;
 }
 
 static uint64_t fwcfg_get_u(uint16_t index, int bytes)
@@ -34,7 +37,10 @@ static uint64_t fwcfg_get_u(uint16_t index, int bytes)
     uint8_t b;
     int i;
 
-    if (fw_override[index] >= 0)
+    if (!fw_override_done)
+        read_cfg_override();
+
+    if (index < FW_CFG_MAX_ENTRY && fw_override[index] >= 0)
 	    return fw_override[index];
 
     spin_lock(&lock);
diff --git a/lib/x86/fwcfg.h b/lib/x86/fwcfg.h
index 88dc7a7..2f17461 100644
--- a/lib/x86/fwcfg.h
+++ b/lib/x86/fwcfg.h
@@ -36,8 +36,6 @@
 
 extern bool no_test_device;
 
-void read_cfg_override(void);
-
 static inline bool test_device_enabled(void)
 {
 	return !no_test_device;
diff --git a/x86/cstart64.S b/x86/cstart64.S
index 23c1bd4..d4e4652 100644
--- a/x86/cstart64.S
+++ b/x86/cstart64.S
@@ -254,8 +254,6 @@ start64:
 	mov %rax, __args(%rip)
 	call __setup_args
 
-	/* Read the configuration before running smp_init */
-	call read_cfg_override
 	call smp_init
 	call enable_x2apic
 
-- 
2.22.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [kvm-unit-tests PATCH] x86: Fix breakage of fw_cfg for 32-bit unit tests
  2019-08-22 23:50 [kvm-unit-tests PATCH] x86: Fix breakage of fw_cfg for 32-bit unit tests Sean Christopherson
@ 2019-08-22 23:55 ` Nadav Amit
  2019-08-22 23:56   ` Sean Christopherson
  0 siblings, 1 reply; 3+ messages in thread
From: Nadav Amit @ 2019-08-22 23:55 UTC (permalink / raw)
  To: Sean Christopherson; +Cc: Paolo Bonzini, Radim Krčmář, kvm

> On Aug 22, 2019, at 4:50 PM, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
> 
> Ensure the fw_cfg overrides are parsed prior consuming any of said
> overrides.  fwcfg_get_u() treats zero as a valid overide value, which
> is slightly problematic since the overrides are in the .bss and thus
> initialized to zero.
> 
> Add a limit check when indexing fw_override so that future code doesn't
> spontaneously explode.
> 
> Cc: Nadav Amit <nadav.amit@gmail.com>
> Fixes: 03b1e4570f967 ("x86: Support environments without test-devices")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> lib/x86/fwcfg.c | 10 ++++++++--
> lib/x86/fwcfg.h |  2 --
> x86/cstart64.S  |  2 --
> 3 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/x86/fwcfg.c b/lib/x86/fwcfg.c
> index d8d797f..06ef62c 100644
> --- a/lib/x86/fwcfg.c
> +++ b/lib/x86/fwcfg.c
> @@ -5,10 +5,11 @@
> static struct spinlock lock;
> 
> static long fw_override[FW_CFG_MAX_ENTRY];
> +static bool fw_override_done;
> 
> bool no_test_device;
> 
> -void read_cfg_override(void)
> +static void read_cfg_override(void)
> {
> 	const char *str;
> 	int i;
> @@ -26,6 +27,8 @@ void read_cfg_override(void)
> 
> 	if ((str = getenv("TEST_DEVICE")))
> 		no_test_device = !atol(str);
> +
> +    fw_override_done = true;
> }
> 
> static uint64_t fwcfg_get_u(uint16_t index, int bytes)
> @@ -34,7 +37,10 @@ static uint64_t fwcfg_get_u(uint16_t index, int bytes)
>     uint8_t b;
>     int i;
> 
> -    if (fw_override[index] >= 0)
> +    if (!fw_override_done)
> +        read_cfg_override();
> +
> +    if (index < FW_CFG_MAX_ENTRY && fw_override[index] >= 0)
> 	    return fw_override[index];

How did that happen? I remember I tested this code with KVM..

Anyhow,

Reviewed-by: Nadav Amit <nadav.amit@gmail.com>

Thanks for fixing it.


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [kvm-unit-tests PATCH] x86: Fix breakage of fw_cfg for 32-bit unit tests
  2019-08-22 23:55 ` Nadav Amit
@ 2019-08-22 23:56   ` Sean Christopherson
  0 siblings, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2019-08-22 23:56 UTC (permalink / raw)
  To: Nadav Amit; +Cc: Paolo Bonzini, Radim Krčmář, kvm

On Thu, Aug 22, 2019 at 04:55:14PM -0700, Nadav Amit wrote:
> > On Aug 22, 2019, at 4:50 PM, Sean Christopherson <sean.j.christopherson@intel.com> wrote:
> > 
> > Ensure the fw_cfg overrides are parsed prior consuming any of said
> > overrides.  fwcfg_get_u() treats zero as a valid overide value, which
> > is slightly problematic since the overrides are in the .bss and thus
> > initialized to zero.
> > 
> > Add a limit check when indexing fw_override so that future code doesn't
> > spontaneously explode.
> > 
> > Cc: Nadav Amit <nadav.amit@gmail.com>
> > Fixes: 03b1e4570f967 ("x86: Support environments without test-devices")
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > ---
> > lib/x86/fwcfg.c | 10 ++++++++--
> > lib/x86/fwcfg.h |  2 --
> > x86/cstart64.S  |  2 --
> > 3 files changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/lib/x86/fwcfg.c b/lib/x86/fwcfg.c
> > index d8d797f..06ef62c 100644
> > --- a/lib/x86/fwcfg.c
> > +++ b/lib/x86/fwcfg.c
> > @@ -5,10 +5,11 @@
> > static struct spinlock lock;
> > 
> > static long fw_override[FW_CFG_MAX_ENTRY];
> > +static bool fw_override_done;
> > 
> > bool no_test_device;
> > 
> > -void read_cfg_override(void)
> > +static void read_cfg_override(void)
> > {
> > 	const char *str;
> > 	int i;
> > @@ -26,6 +27,8 @@ void read_cfg_override(void)
> > 
> > 	if ((str = getenv("TEST_DEVICE")))
> > 		no_test_device = !atol(str);
> > +
> > +    fw_override_done = true;
> > }
> > 
> > static uint64_t fwcfg_get_u(uint16_t index, int bytes)
> > @@ -34,7 +37,10 @@ static uint64_t fwcfg_get_u(uint16_t index, int bytes)
> >     uint8_t b;
> >     int i;
> > 
> > -    if (fw_override[index] >= 0)
> > +    if (!fw_override_done)
> > +        read_cfg_override();
> > +
> > +    if (index < FW_CFG_MAX_ENTRY && fw_override[index] >= 0)
> > 	    return fw_override[index];
> 
> How did that happen? I remember I tested this code with KVM..

It only breaks 32-bit KVM.

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2019-08-22 23:50 [kvm-unit-tests PATCH] x86: Fix breakage of fw_cfg for 32-bit unit tests Sean Christopherson
2019-08-22 23:55 ` Nadav Amit
2019-08-22 23:56   ` Sean Christopherson

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