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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v9 12/15] microcode: reduce memory allocation and copy when creating a patch
On Mon, Aug 19, 2019 at 09:25:25AM +0800, Chao Gao wrote:
> To create a microcode patch from a vendor-specific update,
> allocate_microcode_patch() copied everything from the update.
> It is not efficient. Essentially, we just need to go through
> ucodes in the blob, find the one with the newest revision and
> install it into the microcode_patch. In the process, buffers
> like mc_amd, equiv_cpu_table (on AMD side), and mc (on Intel
> side) can be reused. microcode_patch now is allocated after
> it is sure that there is a matching ucode.
Oh, I think this answers my question on a previous patch.
For future series it would be nice to avoid so many rewrites in the
same series, alloc_microcode_patch is already modified in a previous
patch, just to be removed here. It also makes it harder to follow
what's going on.
>
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> ---
> Changes in v9:
> - new
> ---
> xen/arch/x86/microcode_amd.c | 99
> +++++++++++++++---------------------------
> xen/arch/x86/microcode_intel.c | 65 ++++++++++-----------------
> 2 files changed, 58 insertions(+), 106 deletions(-)
>
> diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
> index 6353323..ec1c2eb 100644
> --- a/xen/arch/x86/microcode_amd.c
> +++ b/xen/arch/x86/microcode_amd.c
> @@ -194,36 +194,6 @@ static bool match_cpu(const struct microcode_patch
> *patch)
> return patch && (microcode_fits(patch->mc_amd) == NEW_UCODE);
> }
>
> -static struct microcode_patch *alloc_microcode_patch(
> - const struct microcode_amd *mc_amd)
> -{
> - struct microcode_patch *microcode_patch = xmalloc(struct
> microcode_patch);
> - struct microcode_amd *cache = xmalloc(struct microcode_amd);
> - void *mpb = xmalloc_bytes(mc_amd->mpb_size);
> - struct equiv_cpu_entry *equiv_cpu_table =
> - xmalloc_bytes(mc_amd->equiv_cpu_table_size);
> -
> - if ( !microcode_patch || !cache || !mpb || !equiv_cpu_table )
> - {
> - xfree(microcode_patch);
> - xfree(cache);
> - xfree(mpb);
> - xfree(equiv_cpu_table);
> - return ERR_PTR(-ENOMEM);
> - }
> -
> - memcpy(mpb, mc_amd->mpb, mc_amd->mpb_size);
> - cache->mpb = mpb;
> - cache->mpb_size = mc_amd->mpb_size;
> - memcpy(equiv_cpu_table, mc_amd->equiv_cpu_table,
> - mc_amd->equiv_cpu_table_size);
> - cache->equiv_cpu_table = equiv_cpu_table;
> - cache->equiv_cpu_table_size = mc_amd->equiv_cpu_table_size;
> - microcode_patch->mc_amd = cache;
> -
> - return microcode_patch;
> -}
> -
> static void free_patch(void *mc)
> {
> struct microcode_amd *mc_amd = mc;
> @@ -320,18 +290,10 @@ static int get_ucode_from_buffer_amd(
> return -EINVAL;
> }
>
> - if ( mc_amd->mpb_size < mpbuf->len )
> - {
> - if ( mc_amd->mpb )
> - {
> - xfree(mc_amd->mpb);
> - mc_amd->mpb_size = 0;
> - }
> - mc_amd->mpb = xmalloc_bytes(mpbuf->len);
> - if ( mc_amd->mpb == NULL )
> - return -ENOMEM;
> - mc_amd->mpb_size = mpbuf->len;
> - }
> + mc_amd->mpb = xmalloc_bytes(mpbuf->len);
> + if ( mc_amd->mpb == NULL )
Nit:
if ( !mc_amd->mpb )
is the usual idiom used in Xen.
> + return -ENOMEM;
> + mc_amd->mpb_size = mpbuf->len;
> memcpy(mc_amd->mpb, mpbuf->data, mpbuf->len);
>
> pr_debug("microcode: CPU%d size %zu, block size %u offset %zu equivID
> %#x rev %#x\n",
> @@ -451,8 +413,9 @@ static struct microcode_patch
> *cpu_request_microcode(const void *buf,
> size_t bufsize)
> {
> struct microcode_amd *mc_amd;
> + struct microcode_header_amd *saved = NULL;
> struct microcode_patch *patch = NULL;
> - size_t offset = 0;
> + size_t offset = 0, saved_size = 0;
> int error = 0;
> unsigned int current_cpu_id;
> unsigned int equiv_cpu_id;
> @@ -542,29 +505,21 @@ static struct microcode_patch
> *cpu_request_microcode(const void *buf,
> while ( (error = get_ucode_from_buffer_amd(mc_amd, buf, bufsize,
> &offset)) == 0 )
> {
> - struct microcode_patch *new_patch = alloc_microcode_patch(mc_amd);
> -
> - if ( IS_ERR(new_patch) )
> - {
> - error = PTR_ERR(new_patch);
> - break;
> - }
> -
> /*
> - * If the new patch covers current CPU, compare patches and store the
> + * If the new ucode covers current CPU, compare ucodes and store the
> * one with higher revision.
> */
> - if ( (microcode_fits(new_patch->mc_amd) != MIS_UCODE) &&
> - (!patch || (compare_patch(new_patch, patch) == NEW_UCODE)) )
> +#define REV_ID(mpb) (((struct microcode_header_amd
> *)(mpb))->processor_rev_id)
> + if ( (microcode_fits(mc_amd) != MIS_UCODE) &&
> + (!saved || (REV_ID(mc_amd->mpb) > REV_ID(saved))) )
> +#undef REV_ID
> {
> - struct microcode_patch *tmp = patch;
> -
> - patch = new_patch;
> - new_patch = tmp;
> + xfree(saved);
> + saved = mc_amd->mpb;
> + saved_size = mc_amd->mpb_size;
> }
> -
> - if ( new_patch )
> - microcode_free_patch(new_patch);
> + else
> + xfree(mc_amd->mpb);
>
> if ( offset >= bufsize )
> break;
> @@ -593,9 +548,25 @@ static struct microcode_patch
> *cpu_request_microcode(const void *buf,
> *(const uint32_t *)(buf + offset) == UCODE_MAGIC )
> break;
> }
> - xfree(mc_amd->mpb);
> - xfree(mc_amd->equiv_cpu_table);
> - xfree(mc_amd);
> +
> + if ( saved )
> + {
> + mc_amd->mpb = saved;
> + mc_amd->mpb_size = saved_size;
> + patch = xmalloc(struct microcode_patch);
> + if ( patch )
> + patch->mc_amd = mc_amd;
> + else
> + {
> + free_patch(mc_amd);
> + error = -ENOMEM;
> + }
> + }
> + else
> + {
> + mc_amd->mpb = NULL;
What's the point in setting mpb to NULL if you are just going to free
mc_amd below?
Also, I'm not sure I understand why you need to free mc_amd, isn't
this buff memory that should be freed by the caller?
ie: in the Intel counterpart below you don't seem to free the mc
cursor used for the get_next_ucode_from_buffer loop.
> + free_patch(mc_amd);
> + }
>
> out:
> if ( error && !patch )
> diff --git a/xen/arch/x86/microcode_intel.c b/xen/arch/x86/microcode_intel.c
> index 96b38f8..ae5759f 100644
> --- a/xen/arch/x86/microcode_intel.c
> +++ b/xen/arch/x86/microcode_intel.c
> @@ -282,25 +282,6 @@ static enum microcode_match_result compare_patch(
> OLD_UCODE;
> }
>
> -static struct microcode_patch *alloc_microcode_patch(
> - const struct microcode_header_intel *mc_header)
> -{
> - unsigned long total_size = get_totalsize(mc_header);
> - void *new_mc = xmalloc_bytes(total_size);
> - struct microcode_patch *new_patch = xmalloc(struct microcode_patch);
> -
> - if ( !new_patch || !new_mc )
> - {
> - xfree(new_patch);
> - xfree(new_mc);
> - return ERR_PTR(-ENOMEM);
> - }
> - memcpy(new_mc, mc_header, total_size);
> - new_patch->mc_intel = new_mc;
> -
> - return new_patch;
> -}
> -
> static int apply_microcode(const struct microcode_patch *patch)
> {
> unsigned long flags;
> @@ -379,47 +360,47 @@ static struct microcode_patch
> *cpu_request_microcode(const void *buf,
> {
> long offset = 0;
> int error = 0;
> - void *mc;
> + struct microcode_intel *mc, *saved = NULL;
> struct microcode_patch *patch = NULL;
>
> - while ( (offset = get_next_ucode_from_buffer(&mc, buf, size, offset)) >
> 0 )
> + while ( (offset = get_next_ucode_from_buffer((void **)&mc, buf,
> + size, offset)) > 0 )
> {
> - struct microcode_patch *new_patch;
> -
> error = microcode_sanity_check(mc);
> if ( error )
> - break;
> -
> - new_patch = alloc_microcode_patch(mc);
> - if ( IS_ERR(new_patch) )
> {
> - error = PTR_ERR(new_patch);
> + xfree(mc);
> break;
> }
>
> /*
> - * If the new patch covers current CPU, compare patches and store the
> + * If the new update covers current CPU, compare updates and store
> the
> * one with higher revision.
> */
> - if ( (microcode_update_match(&new_patch->mc_intel->hdr) !=
> MIS_UCODE) &&
> - (!patch || (compare_patch(new_patch, patch) == NEW_UCODE)) )
> + if ( (microcode_update_match(&mc->hdr) != MIS_UCODE) &&
> + (!saved || (mc->hdr.rev > saved->hdr.rev)) )
> {
> - struct microcode_patch *tmp = patch;
> -
> - patch = new_patch;
> - new_patch = tmp;
> + xfree(saved);
> + saved = mc;
> }
> -
> - if ( new_patch )
> - microcode_free_patch(new_patch);
> -
> - xfree(mc);
> + else
> + xfree(mc);
> }
> - if ( offset > 0 )
> - xfree(mc);
> if ( offset < 0 )
> error = offset;
>
> + if ( saved )
> + {
> + patch = xmalloc(struct microcode_patch);
> + if ( patch )
> + patch->mc_intel = saved;
> + else
> + {
> + xfree(saved);
> + error = -ENOMEM;
> + }
> + }
> +
The above code looks suspiciously similar to the AMD
cpu_request_microcode counterpart, which makes me think it could be
further abstracted in order to reduce this duplication. In any case,
this can be done in a follow up patch.
Thanks, Roger.
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