From 2609b6e6d52783f1a58e4c50832a9c6ebd671336 Mon Sep 17 00:00:00 2001 From: Henry Wang Date: Tue, 9 Aug 2022 06:39:23 +0000 Subject: [PATCH 1/4] libxl, docs: Use arch-specific default paging memory The default paging memory (descibed in `shadow_memory` entry in xl config) in libxl is used to determine the memory pool size for xl guests. Currently this size is only used for x86, and contains a part of RAM to shadow the resident processes. Since on Arm there is no shadow mode guests, so the part of RAM to shadow the resident processes is not necessary. Therefore, this commit splits the function `libxl_get_required_shadow_memory()` to arch specific helpers and renamed the helper to `libxl__arch_get_required_paging_memory()`. On x86, this helper calls the original value from `libxl_get_required_shadow_memory()` so no functional change intended. On Arm, this helper returns 1MB per vcpu plus 4KB per MiB of RAM for the P2M map. Also update the xl.cfg documentation to add Arm documentation according to code changes and correct the comment style following Xen coding style. This is part of CVE-2022-33747 / XSA-409. Suggested-by: Julien Grall Signed-off-by: Henry Wang Reviewed-by: Anthony PERARD --- docs/man/xl.cfg.5.pod.in | 5 +++++ tools/libxl/libxl_arch.h | 4 ++++ tools/libxl/libxl_arm.c | 12 ++++++++++++ tools/libxl/libxl_utils.c | 9 ++------- tools/libxl/libxl_x86.c | 12 ++++++++++++ 5 files changed, 35 insertions(+), 7 deletions(-) diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in index 0532739c1fff..2224080b30ce 100644 --- a/docs/man/xl.cfg.5.pod.in +++ b/docs/man/xl.cfg.5.pod.in @@ -1803,6 +1803,11 @@ are not using hardware assisted paging (i.e. you are using shadow mode) and your guest workload consists of a very large number of similar processes then increasing this value may improve performance. +On Arm, this field is used to determine the size of the guest P2M pages +pool, and the default value is 1MB per vCPU plus 4KB per MB of RAM for +the P2M map. Users should adjust this value if bigger P2M pool size is +needed. + =back =head3 Processor and Platform Features diff --git a/tools/libxl/libxl_arch.h b/tools/libxl/libxl_arch.h index 6a91775b9e20..b09f868490ac 100644 --- a/tools/libxl/libxl_arch.h +++ b/tools/libxl/libxl_arch.h @@ -83,6 +83,10 @@ int libxl__arch_extra_memory(libxl__gc *gc, const libxl_domain_build_info *info, uint64_t *out); +_hidden +unsigned long libxl__arch_get_required_paging_memory(unsigned long maxmem_kb, + unsigned int smp_cpus); + #if defined(__i386__) || defined(__x86_64__) #define LAPIC_BASE_ADDRESS 0xfee00000 diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c index 34f8a29056db..f4b3dc8e7139 100644 --- a/tools/libxl/libxl_arm.c +++ b/tools/libxl/libxl_arm.c @@ -153,6 +153,18 @@ out: return rc; } +unsigned long libxl__arch_get_required_paging_memory(unsigned long maxmem_kb, + unsigned int smp_cpus) +{ + /* + * 256 pages (1MB) per vcpu, + * plus 1 page per MiB of RAM for the P2M map, + * This is higher than the minimum that Xen would allocate if no value + * were given (but the Xen minimum is for safety, not performance). + */ + return 4 * (256 * smp_cpus + maxmem_kb / 1024); +} + static struct arch_info { const char *guest_type; const char *timer_compat; diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c index b039143b8aef..e18b1524ef78 100644 --- a/tools/libxl/libxl_utils.c +++ b/tools/libxl/libxl_utils.c @@ -18,6 +18,7 @@ #include #include "libxl_internal.h" +#include "libxl_arch.h" #include "_paths.h" #ifndef LIBXL_HAVE_NONCONST_LIBXL_BASENAME_RETURN_VALUE @@ -39,13 +40,7 @@ char *libxl_basename(const char *name) unsigned long libxl_get_required_shadow_memory(unsigned long maxmem_kb, unsigned int smp_cpus) { - /* 256 pages (1MB) per vcpu, - plus 1 page per MiB of RAM for the P2M map, - plus 1 page per MiB of RAM to shadow the resident processes. - This is higher than the minimum that Xen would allocate if no value - were given (but the Xen minimum is for safety, not performance). - */ - return 4 * (256 * smp_cpus + 2 * (maxmem_kb / 1024)); + return libxl__arch_get_required_paging_memory(maxmem_kb, smp_cpus); } char *libxl_domid_to_name(libxl_ctx *ctx, uint32_t domid) diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c index 07c7b05e0d36..0ad455301d88 100644 --- a/tools/libxl/libxl_x86.c +++ b/tools/libxl/libxl_x86.c @@ -852,6 +852,18 @@ int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc, return rc; } +unsigned long libxl__arch_get_required_paging_memory(unsigned long maxmem_kb, + unsigned int smp_cpus) +{ + /* + * 256 pages (1MB) per vcpu, + * plus 1 page per MiB of RAM for the P2M map, + * plus 1 page per MiB of RAM to shadow the resident processes. + * This is higher than the minimum that Xen would allocate if no value + * were given (but the Xen minimum is for safety, not performance). + */ + return 4 * (256 * smp_cpus + 2 * (maxmem_kb / 1024)); +} /* * Local variables: -- 2.37.1