* [PATCH v2] xenpv: don't BUG when failing to setup NMI callback
@ 2014-06-16 11:07 Vitaly Kuznetsov
2014-06-16 14:22 ` Konrad Rzeszutek Wilk
2014-06-16 16:37 ` [Xen-devel] " David Vrabel
0 siblings, 2 replies; 3+ messages in thread
From: Vitaly Kuznetsov @ 2014-06-16 11:07 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk, Boris Ostrovsky, David Vrabel
Cc: x86, xen-devel, linux-kernel, Andrew Jones
some old Xen hypervisors (prior to 3.2) forbid DomUs to register
NMI callbacks. E.g. we have the following code in xen-3.1:
if ( (d->domain_id != 0) || (v->vcpu_id != 0) )
return -EINVAL;
Commit 6efa20e49b9cb1db1ab66870cc37323474a75a13 introduced kernel
crash in case PV guest fails to register NMI callback. All x86_64
PV guests will fail to boot on top of such hypervisors (RHEL5
example):
(XEN) traps.c:405:d7 Unhandled invalid opcode fault/trap [#6] in domain 7 on VCPU 0 [ec=0000]
(XEN) domain_crash_sync called from entry.S
(XEN) Domain 7 (vcpu#0) crashed on cpu#3:
(XEN) ----[ Xen-3.1.2-389.el5 x86_64 debug=n Not tainted ]----
(XEN) CPU: 3
(XEN) RIP: e033:[<ffffffff81004d96>]
(XEN) RFLAGS: 0000000000000282 CONTEXT: guest
(XEN) rax: ffffffffffffffea rbx: 0000000000000000 rcx: 0000000000000002
(XEN) rdx: 0000000000000001 rsi: ffffffff81b0fe28 rdi: 0000000000000000
(XEN) rbp: ffffffff81b0fe40 rsp: ffffffff81b0fde8 r8: 0000000000000000
(XEN) r9: ffffffff81b0fdd0 r10: 0000000000007ff0 r11: 00000000ffffffff
(XEN) r12: ffffffff81d65900 r13: 0000000000000000 r14: 0000000000000000
(XEN) r15: 0000000000000000 cr0: 0000000080050033 cr4: 00000000000026b0
(XEN) cr3: 000000013a263000 cr2: 0000000000000000
(XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033
...
However it is possible to proceed without NMI callback registered.
Changes in v2:
- skip nmi in cvt_gate_to_trap() for Xen < 3.2
- do not call xen_enable_nmi() when running under Xen < 3.2
- never BUG() in xen_enable_nmi()
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/xen/enlighten.c | 9 +++++----
arch/x86/xen/setup.c | 17 ++++++++++++++---
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index f17b292..60ec5ef 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -746,12 +746,13 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
*/
;
#endif
- } else if (addr == (unsigned long)nmi)
+ } else if (addr == (unsigned long)nmi) {
/*
- * Use the native version as well.
+ * Use the native version as well but require Xen >= 3.2
*/
- ;
- else {
+ if (!xen_running_on_version_or_later(3, 2))
+ return 0;
+ } else {
/* Some other trap using IST? */
if (WARN_ON(val->ist != 0))
return 0;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 821a11a..fdc73d3 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -593,8 +593,14 @@ void xen_enable_syscall(void)
void xen_enable_nmi(void)
{
#ifdef CONFIG_X86_64
- if (register_callback(CALLBACKTYPE_nmi, (char *)nmi))
- BUG();
+ int ret;
+
+ ret = register_callback(CALLBACKTYPE_nmi, (char *)nmi);
+ if (ret != 0) {
+ /* Hypervisor probably forbids us to register NMI callback or
+ some other error happened */
+ pr_warn("xen: failed to register NMI callback: %d\n", ret);
+ }
#endif
}
void __init xen_pvmmu_arch_setup(void)
@@ -611,7 +617,12 @@ void __init xen_pvmmu_arch_setup(void)
xen_enable_sysenter();
xen_enable_syscall();
- xen_enable_nmi();
+
+ /* Xen versions prior to 3.2 forbid DomUs to register NMI callbacks */
+ if (xen_running_on_version_or_later(3, 2))
+ xen_enable_nmi();
+ else
+ pr_warn("xen: skipping NMI callback registration for Xen < 3.2");
}
/* This function is not called for HVM domains */
--
1.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] xenpv: don't BUG when failing to setup NMI callback
2014-06-16 11:07 [PATCH v2] xenpv: don't BUG when failing to setup NMI callback Vitaly Kuznetsov
@ 2014-06-16 14:22 ` Konrad Rzeszutek Wilk
2014-06-16 16:37 ` [Xen-devel] " David Vrabel
1 sibling, 0 replies; 3+ messages in thread
From: Konrad Rzeszutek Wilk @ 2014-06-16 14:22 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: Boris Ostrovsky, David Vrabel, x86, xen-devel, linux-kernel,
Andrew Jones
On Mon, Jun 16, 2014 at 01:07:00PM +0200, Vitaly Kuznetsov wrote:
> some old Xen hypervisors (prior to 3.2) forbid DomUs to register
> NMI callbacks. E.g. we have the following code in xen-3.1:
>
> if ( (d->domain_id != 0) || (v->vcpu_id != 0) )
> return -EINVAL;
>
> Commit 6efa20e49b9cb1db1ab66870cc37323474a75a13 introduced kernel
> crash in case PV guest fails to register NMI callback. All x86_64
> PV guests will fail to boot on top of such hypervisors (RHEL5
> example):
>
> (XEN) traps.c:405:d7 Unhandled invalid opcode fault/trap [#6] in domain 7 on VCPU 0 [ec=0000]
> (XEN) domain_crash_sync called from entry.S
> (XEN) Domain 7 (vcpu#0) crashed on cpu#3:
> (XEN) ----[ Xen-3.1.2-389.el5 x86_64 debug=n Not tainted ]----
> (XEN) CPU: 3
> (XEN) RIP: e033:[<ffffffff81004d96>]
> (XEN) RFLAGS: 0000000000000282 CONTEXT: guest
> (XEN) rax: ffffffffffffffea rbx: 0000000000000000 rcx: 0000000000000002
> (XEN) rdx: 0000000000000001 rsi: ffffffff81b0fe28 rdi: 0000000000000000
> (XEN) rbp: ffffffff81b0fe40 rsp: ffffffff81b0fde8 r8: 0000000000000000
> (XEN) r9: ffffffff81b0fdd0 r10: 0000000000007ff0 r11: 00000000ffffffff
> (XEN) r12: ffffffff81d65900 r13: 0000000000000000 r14: 0000000000000000
> (XEN) r15: 0000000000000000 cr0: 0000000080050033 cr4: 00000000000026b0
> (XEN) cr3: 000000013a263000 cr2: 0000000000000000
> (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: e02b cs: e033
> ...
>
> However it is possible to proceed without NMI callback registered.
>
> Changes in v2:
> - skip nmi in cvt_gate_to_trap() for Xen < 3.2
> - do not call xen_enable_nmi() when running under Xen < 3.2
> - never BUG() in xen_enable_nmi()
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Awesome!
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
David, if you don't get to stash this patch in the queue - I can
do it on Friday.
> ---
> arch/x86/xen/enlighten.c | 9 +++++----
> arch/x86/xen/setup.c | 17 ++++++++++++++---
> 2 files changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index f17b292..60ec5ef 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -746,12 +746,13 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
> */
> ;
> #endif
> - } else if (addr == (unsigned long)nmi)
> + } else if (addr == (unsigned long)nmi) {
> /*
> - * Use the native version as well.
> + * Use the native version as well but require Xen >= 3.2
> */
> - ;
> - else {
> + if (!xen_running_on_version_or_later(3, 2))
> + return 0;
> + } else {
> /* Some other trap using IST? */
> if (WARN_ON(val->ist != 0))
> return 0;
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 821a11a..fdc73d3 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -593,8 +593,14 @@ void xen_enable_syscall(void)
> void xen_enable_nmi(void)
> {
> #ifdef CONFIG_X86_64
> - if (register_callback(CALLBACKTYPE_nmi, (char *)nmi))
> - BUG();
> + int ret;
> +
> + ret = register_callback(CALLBACKTYPE_nmi, (char *)nmi);
> + if (ret != 0) {
> + /* Hypervisor probably forbids us to register NMI callback or
> + some other error happened */
> + pr_warn("xen: failed to register NMI callback: %d\n", ret);
> + }
> #endif
> }
> void __init xen_pvmmu_arch_setup(void)
> @@ -611,7 +617,12 @@ void __init xen_pvmmu_arch_setup(void)
>
> xen_enable_sysenter();
> xen_enable_syscall();
> - xen_enable_nmi();
> +
> + /* Xen versions prior to 3.2 forbid DomUs to register NMI callbacks */
> + if (xen_running_on_version_or_later(3, 2))
> + xen_enable_nmi();
> + else
> + pr_warn("xen: skipping NMI callback registration for Xen < 3.2");
> }
>
> /* This function is not called for HVM domains */
> --
> 1.9.3
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xen-devel] [PATCH v2] xenpv: don't BUG when failing to setup NMI callback
2014-06-16 11:07 [PATCH v2] xenpv: don't BUG when failing to setup NMI callback Vitaly Kuznetsov
2014-06-16 14:22 ` Konrad Rzeszutek Wilk
@ 2014-06-16 16:37 ` David Vrabel
1 sibling, 0 replies; 3+ messages in thread
From: David Vrabel @ 2014-06-16 16:37 UTC (permalink / raw)
To: Vitaly Kuznetsov, Konrad Rzeszutek Wilk, Boris Ostrovsky,
David Vrabel
Cc: xen-devel, Andrew Jones, x86, linux-kernel
On 16/06/14 12:07, Vitaly Kuznetsov wrote:
>
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -746,12 +746,13 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
> */
> ;
> #endif
> - } else if (addr == (unsigned long)nmi)
> + } else if (addr == (unsigned long)nmi) {
> /*
> - * Use the native version as well.
> + * Use the native version as well but require Xen >= 3.2
> */
> - ;
> - else {
> + if (!xen_running_on_version_or_later(3, 2))
> + return 0;
> + } else {
The end result of this looked odd so I played around with it a bit and
it turns out that the register_callback for the NMI is entirely unneeded
(since we set the NMI callback via the write_idt pv-op and it's also
broken since it only sets the callback on the current VCPU.
I'm preparing an alternate patch, but I do not have a Xen 3.1 install I
can test with.
David
^ permalink raw reply [flat|nested] 3+ messages in thread
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2014-06-16 11:07 [PATCH v2] xenpv: don't BUG when failing to setup NMI callback Vitaly Kuznetsov
2014-06-16 14:22 ` Konrad Rzeszutek Wilk
2014-06-16 16:37 ` [Xen-devel] " David Vrabel
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