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SubjectRe: [PATCH 1/2] x86/microcode: Update late microcode in parallel
On Mon, Aug 26, 2019 at 01:32:48PM -0700, Raj, Ashok wrote:
> On Mon, Aug 26, 2019 at 08:53:05AM -0400, Boris Ostrovsky wrote:
> > On 8/24/19 4:53 AM, Borislav Petkov wrote:
> > >
> > > +wait_for_siblings:
> > > + if (__wait_for_cpus(&late_cpus_out, NSEC_PER_SEC))
> > > + panic("Timeout during microcode update!\n");
> > > +
> > > /*
> > > - * Increase the wait timeout to a safe value here since we're
> > > - * serializing the microcode update and that could take a while on a
> > > - * large number of CPUs. And that is fine as the *actual* timeout will
> > > - * be determined by the last CPU finished updating and thus cut short.
> > > + * At least one thread has completed update on each core.
> > > + * For others, simply call the update to make sure the
> > > + * per-cpu cpuinfo can be updated with right microcode
> > > + * revision.
> >
> >
> > What is the advantage of having those other threads go through
> > find_patch() and (in Intel case) intel_get_microcode_revision() (which
> > involves two MSR accesses) vs. having the master sibling update slaves'
> > microcode revisions? There are only two things that need to be updated,
> > uci->cpu_sig.rev and c->microcode.
> >
>
> True, yes we could do that. But there is some warm and comfy feeling
> that you really read the revision from the thread local copy of the revision
> and it matches what was updated in the other thread sibling rather than
> just hardcoding the fixup's. The code looks clean in the sense it looks like
> you are attempting to upgrade but the new revision is reflected correctly
> and you skip the update.
>
> But if you feel complelled, i'm not opposed to it as long as Boris is
> happy with the changes :-).



Something like this. I only lightly tested this but if there is interest
I can test it more.



From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Date: Tue, 27 Aug 2019 08:26:08 -0400
Subject: [PATCH 2/2] x86/microcode: Have master sibling update slaves' data

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
arch/x86/kernel/cpu/microcode/amd.c | 21 ++++--------------
arch/x86/kernel/cpu/microcode/core.c | 40 ++++++++++++++++++++---------------
arch/x86/kernel/cpu/microcode/intel.c | 18 +++-------------
3 files changed, 30 insertions(+), 49 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index a0e52bd..a365f72 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -668,11 +668,9 @@ static int collect_cpu_info_amd(int cpu, struct cpu_signature *csig)

static enum ucode_state apply_microcode_amd(int cpu)
{
- struct cpuinfo_x86 *c = &cpu_data(cpu);
struct microcode_amd *mc_amd;
struct ucode_cpu_info *uci;
struct ucode_patch *p;
- enum ucode_state ret;
u32 rev, dummy;

BUG_ON(raw_smp_processor_id() != cpu);
@@ -689,10 +687,8 @@ static enum ucode_state apply_microcode_amd(int cpu)
rdmsr(MSR_AMD64_PATCH_LEVEL, rev, dummy);

/* need to apply patch? */
- if (rev >= mc_amd->hdr.patch_id) {
- ret = UCODE_OK;
- goto out;
- }
+ if (rev >= mc_amd->hdr.patch_id)
+ return UCODE_OK;

if (__apply_microcode_amd(mc_amd)) {
pr_err("CPU%d: update failed for patch_level=0x%08x\n",
@@ -700,20 +696,11 @@ static enum ucode_state apply_microcode_amd(int cpu)
return UCODE_ERROR;
}

- rev = mc_amd->hdr.patch_id;
- ret = UCODE_UPDATED;
-
- pr_info("CPU%d: new patch_level=0x%08x\n", cpu, rev);
-
-out:
uci->cpu_sig.rev = rev;
- c->microcode = rev;

- /* Update boot_cpu_data's revision too, if we're on the BSP: */
- if (c->cpu_index == boot_cpu_data.cpu_index)
- boot_cpu_data.microcode = rev;
+ pr_info("CPU%d: new patch_level=0x%08x\n", cpu, rev);

- return ret;
+ return UCODE_UPDATED;
}

static size_t install_equiv_cpu_table(const u8 *buf, size_t buf_size)
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b..09643c6 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -551,6 +551,8 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
static int __reload_late(void *info)
{
int cpu = smp_processor_id();
+ struct cpuinfo_x86 *c = &cpu_data(cpu);
+ bool bsp = (c->cpu_index == boot_cpu_data.cpu_index);
enum ucode_state err;
int ret = 0;

@@ -568,30 +570,34 @@ static int __reload_late(void *info)
* loading attempts happen on multiple threads of an SMT core. See
* below.
*/
- if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu)
+ if (cpumask_first(topology_sibling_cpumask(cpu)) == cpu) {
apply_microcode_local(&err);
- else
- goto wait_for_siblings;

- if (err > UCODE_NFOUND) {
- pr_warn("Error reloading microcode on CPU %d\n", cpu);
- ret = -1;
- } else if (err == UCODE_UPDATED || err == UCODE_OK) {
- ret = 1;
+ if (err > UCODE_NFOUND) {
+ pr_warn("Error reloading microcode on CPU %d\n", cpu);
+ ret = -1;
+ } else if (err == UCODE_UPDATED || err == UCODE_OK) {
+ struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
+ int sibling, rev = uci->cpu_sig.rev;
+
+ /* All siblings have same revision */
+ for_each_cpu(sibling, topology_sibling_cpumask(cpu)) {
+ c = &cpu_data(sibling);
+ uci = ucode_cpu_info + sibling;
+
+ uci->cpu_sig.rev = rev;
+ c->microcode = rev;
+ }
+
+ ret = 1;
+ }
}

-wait_for_siblings:
if (__wait_for_cpus(&late_cpus_out, NSEC_PER_SEC))
panic("Timeout during microcode update!\n");

- /*
- * At least one thread has completed update on each core.
- * For others, simply call the update to make sure the
- * per-cpu cpuinfo can be updated with right microcode
- * revision.
- */
- if (cpumask_first(topology_sibling_cpumask(cpu)) != cpu)
- apply_microcode_local(&err);
+ if (bsp)
+ boot_cpu_data.microcode = c->microcode;

return ret;
}
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index ce799cf..04e9aa2 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -790,9 +790,7 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
static enum ucode_state apply_microcode_intel(int cpu)
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
- struct cpuinfo_x86 *c = &cpu_data(cpu);
struct microcode_intel *mc;
- enum ucode_state ret;
static int prev_rev;
u32 rev;

@@ -814,10 +812,8 @@ static enum ucode_state apply_microcode_intel(int cpu)
* already.
*/
rev = intel_get_microcode_revision();
- if (rev >= mc->hdr.rev) {
- ret = UCODE_OK;
- goto out;
- }
+ if (rev >= mc->hdr.rev)
+ return UCODE_OK;

/*
* Writeback and invalidate caches before updating microcode to avoid
@@ -845,17 +841,9 @@ static enum ucode_state apply_microcode_intel(int cpu)
prev_rev = rev;
}

- ret = UCODE_UPDATED;
-
-out:
uci->cpu_sig.rev = rev;
- c->microcode = rev;
-
- /* Update boot_cpu_data's revision too, if we're on the BSP: */
- if (c->cpu_index == boot_cpu_data.cpu_index)
- boot_cpu_data.microcode = rev;

- return ret;
+ return UCODE_UPDATED;
}

static enum ucode_state generic_load_microcode(int cpu, struct iov_iter *iter)
--
1.8.3.1


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