From 9452246e59a5f16f44fdf9a7d514b947faf1d5fc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Date: Mon, 16 Jan 2023 18:46:05 +0100 Subject: [PATCH 5/9] s390x/pv: Implement a CGS check helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Cédric Le Goater RH-MergeRequest: 139: s390x/pv: Implement a CGS check helper RH-Bugzilla: 2122523 RH-Acked-by: Thomas Huth RH-Acked-by: Cornelia Huck RH-Acked-by: David Hildenbrand RH-Commit: [1/1] 8551ce772b10de653b4e1c8be60aae60ec98b421 (clegoate/qemu-kvm-c9s) When a protected VM is started with the maximum number of CPUs (248), the service call providing information on the CPUs requires more buffer space than allocated and QEMU disgracefully aborts : LOADPARM=[........] Using virtio-blk. Using SCSI scheme. ................................................................................... qemu-system-s390x: KVM_S390_MEM_OP failed: Argument list too long When protected virtualization is initialized, compute the maximum number of vCPUs supported by the machine and return useful information to the user before the machine starts in case of error. Suggested-by: Thomas Huth Reviewed-by: Thomas Huth Signed-off-by: Cédric Le Goater Message-Id: <20230116174607.2459498-2-clg@kaod.org> Signed-off-by: Thomas Huth (cherry picked from commit 75d7150c636569f6687f7e70a33be893be43eb5f) Signed-off-by: Cédric Le Goater --- hw/s390x/pv.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c index 8dfe92d8df..8a1c71436b 100644 --- a/hw/s390x/pv.c +++ b/hw/s390x/pv.c @@ -20,6 +20,7 @@ #include "exec/confidential-guest-support.h" #include "hw/s390x/ipl.h" #include "hw/s390x/pv.h" +#include "hw/s390x/sclp.h" #include "target/s390x/kvm/kvm_s390x.h" static bool info_valid; @@ -249,6 +250,41 @@ struct S390PVGuestClass { ConfidentialGuestSupportClass parent_class; }; +/* + * If protected virtualization is enabled, the amount of data that the + * Read SCP Info Service Call can use is limited to one page. The + * available space also depends on the Extended-Length SCCB (ELS) + * feature which can take more buffer space to store feature + * information. This impacts the maximum number of CPUs supported in + * the machine. + */ +static uint32_t s390_pv_get_max_cpus(void) +{ + int offset_cpu = s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB) ? + offsetof(ReadInfo, entries) : SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET; + + return (TARGET_PAGE_SIZE - offset_cpu) / sizeof(CPUEntry); +} + +static bool s390_pv_check_cpus(Error **errp) +{ + MachineState *ms = MACHINE(qdev_get_machine()); + uint32_t pv_max_cpus = s390_pv_get_max_cpus(); + + if (ms->smp.max_cpus > pv_max_cpus) { + error_setg(errp, "Protected VMs support a maximum of %d CPUs", + pv_max_cpus); + return false; + } + + return true; +} + +static bool s390_pv_guest_check(ConfidentialGuestSupport *cgs, Error **errp) +{ + return s390_pv_check_cpus(errp); +} + int s390_pv_kvm_init(ConfidentialGuestSupport *cgs, Error **errp) { if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) { @@ -261,6 +297,10 @@ int s390_pv_kvm_init(ConfidentialGuestSupport *cgs, Error **errp) return -1; } + if (!s390_pv_guest_check(cgs, errp)) { + return -1; + } + cgs->ready = true; return 0; -- 2.31.1