78 lines
3.0 KiB
Diff
78 lines
3.0 KiB
Diff
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# Commit e294a0c3af9f4443dc692b180fb1771b1cb075e8
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# Date 2015-10-29 15:11:51 +0000
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# Author Ian Jackson <ian.jackson@eu.citrix.com>
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# Committer Ian Jackson <Ian.Jackson@eu.citrix.com>
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libxl: adjust PoD target by memory fudge, too
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PoD guests need to balloon at least as far as required by PoD, or risk
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crashing. Currently they don't necessarily know what the right value
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is, because our memory accounting is (at the very least) confusing.
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Apply the memory limit fudge factor to the in-hypervisor PoD memory
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target, too. This will increase the size of the guest's PoD cache by
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the fudge factor LIBXL_MAXMEM_CONSTANT (currently 1Mby). This ensures
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that even with a slightly-off balloon driver, the guest will be
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stable even under memory pressure.
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There are two call sites of xc_domain_set_pod_target that need fixing:
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The one in libxl_set_memory_target is straightforward.
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The one in xc_hvm_build_x86.c:setup_guest is more awkward. Simply
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setting the PoD target differently does not work because the various
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amounts of memory during domain construction no longer match up.
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Instead, we adjust the guest memory target in xenstore (but only for
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PoD guests).
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This introduces a 1Mby discrepancy between the balloon target of a PoD
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guest at boot, and the target set by an apparently-equivalent `xl
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mem-set' (or similar) later. This approach is low-risk for a security
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fix but we need to fix this up properly in xen.git#staging and
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probably also in stable trees.
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This is XSA-153.
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Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
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(cherry picked from commit 56fb5fd62320eb40a7517206f9706aa9188d6f7b)
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--- a/tools/libxl/libxl.c
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+++ b/tools/libxl/libxl.c
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@@ -4815,7 +4815,7 @@ retry_transaction:
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}
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rc = xc_domain_set_pod_target(ctx->xch, domid,
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- new_target_memkb / 4, NULL, NULL, NULL);
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+ (new_target_memkb + LIBXL_MAXMEM_CONSTANT) / 4, NULL, NULL, NULL);
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if (rc != 0) {
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LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
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"xc_domain_set_pod_target domid=%d, memkb=%d "
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--- a/tools/libxl/libxl_dom.c
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+++ b/tools/libxl/libxl_dom.c
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@@ -486,6 +486,7 @@ int libxl__build_post(libxl__gc *gc, uin
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xs_transaction_t t;
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char **ents;
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int i, rc;
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+ int64_t mem_target_fudge;
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if (info->num_vnuma_nodes && !info->num_vcpu_soft_affinity) {
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rc = set_vnuma_affinity(gc, domid, info);
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@@ -518,11 +519,17 @@ int libxl__build_post(libxl__gc *gc, uin
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}
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}
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+ mem_target_fudge =
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+ (info->type == LIBXL_DOMAIN_TYPE_HVM &&
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+ info->max_memkb > info->target_memkb)
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+ ? LIBXL_MAXMEM_CONSTANT : 0;
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+
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ents = libxl__calloc(gc, 12 + (info->max_vcpus * 2) + 2, sizeof(char *));
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ents[0] = "memory/static-max";
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ents[1] = GCSPRINTF("%"PRId64, info->max_memkb);
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ents[2] = "memory/target";
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- ents[3] = GCSPRINTF("%"PRId64, info->target_memkb - info->video_memkb);
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+ ents[3] = GCSPRINTF("%"PRId64, info->target_memkb - info->video_memkb
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+ - mem_target_fudge);
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ents[4] = "memory/videoram";
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ents[5] = GCSPRINTF("%"PRId64, info->video_memkb);
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ents[6] = "domid";
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