On Sun, Feb 11, 2024 at 07:38:39PM +0100, Alejandro Colomar wrote: > Hi Charlie, > > On Wed, Jan 24, 2024 at 06:59:04PM -0800, Charlie Jenkins wrote: > > I have proposed and documented the PR_RISCV_SET_ICACHE_FLUSH_CTX flag > > for prctl(2) to LKML. It has been reviewed and is expected to land > > during the Linux version 6.9 merge window. This adds the relevant > > documentation from that patch. > > > > Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx> > > This patch triggers a few warnings: > > $ make lint check -k > TROFF .tmp/man/man2/prctl.2.cat.set > an.tmac:man2/prctl.2:1155: style: .IR expects at least 2 arguments, got 1 > an.tmac:man2/prctl.2:1157: style: .IR expects at least 2 arguments, got 1 > an.tmac:man2/prctl.2:1179: style: .IR expects at least 2 arguments, got 1 > an.tmac:man2/prctl.2:1196: style: .IR expects at least 2 arguments, got 1 > make: *** [share/mk/build/catman.mk:54: .tmp/man/man2/prctl.2.cat.set] Error 1 > make: *** Deleting file '.tmp/man/man2/prctl.2.cat.set' > make: Target 'check' not remade because of errors. > > See <CONTRIBUTING.d/lint> for that. These lint errors didn't show up when I ran it, I must have some bad configuration. > > > --- > > I have proposed and documented the PR_RISCV_SET_ICACHE_FLUSH_CTX > > flag for prctl(2) to LKML. It has been reviewed and is expected to land > > during the Linux version 6.9 merge window. > > --- > > man2/prctl.2 | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 58 insertions(+) > > > > diff --git a/man2/prctl.2 b/man2/prctl.2 > > index f1604a7cb..2889a7195 100644 > > --- a/man2/prctl.2 > > +++ b/man2/prctl.2 > > @@ -1147,6 +1147,64 @@ For further information, see the kernel source file > > (or > > .I Documentation/security/Yama.txt > > before Linux 4.13). > > +.\" prctl PR_RISCV_SET_ICACHE_FLUSH_CTX > > +.TP > > +.BR PR_RISCV_SET_ICACHE_FLUSH_CTX " (since Linux 6.9, RISC-V only)" > > +Enable/disable icache flushing instructions in userspace. The ctx and the > > 'ctx' isn't a common word. The first time you mention it you should > probably say what it means. For example: "The context (ctx) and > the ..." and later just use ctx. > > > +scope can be provided using > > +.IR arg2 > > This should be I, not IR. > > > +and > > +.IR arg3 > > +respectively. When scope is set to > > Please use semantic newlines. See man-pages(7): > > Use semantic newlines > In the source of a manual page, new sentences should be started > on new lines, long sentences should be split into lines at clause > breaks (commas, semicolons, colons, and so on), and long clauses > should be split at phrase boundaries. This convention, sometimes > known as "semantic newlines", makes it easier to see the effect > of patches, which often operate at the level of individual sen‐ > tences, clauses, or phrases. > > > +.B PR_RISCV_SCOPE_PER_PROCESS , > > This should be BR, not B. See groff_man(7). > > > +all threads in the process are permitted to emit icache flushing > > +instructions. Whenever any thread in the process is migrated, the > > +corresponding hart's icache will be guaranteed to be consistent with > > +instruction storage. Note this does not enforce any guarantees outside of > > 'Note' is superfluous. You can just remove that word. "This does not > enforce ...". > > > +migration. If a thread modifies an instruction that another thread may > > +attempt to execute, the other thread must still emit an icache flushing > > +instruction before attempting to execute the potentially modified > > +instruction. This must be performed by the userspace program. > > We say "user space"; two words (see man-pages(7)). In this case, since > it's an adjective, it would be "user-space", with a hyphen. > > > +.IP > > +In per-thread context (eg. scope is set to > > +.B PR_RISCV_SCOPE_PER_THREAD ) > > The comma should go with the parenthesis. Otherwise, you'll see a > spurious space in between. > > > +, only the thread calling this function is permitted to emit icache > > +flushing instructions. When the thread is migrated, the corresponding > > +hart's icache will be guaranteed to be consistent with instruction storage. > > +.IP > > +On kernels configured without SMP, this function is a nop as migrations > > +across harts will not occur. > > +.IP > > +The following values for > > +.IR arg2 > > +can be specified: > > +.RS > > +.TP > > +.BR PR_RISCV_CTX_SW_FENCEI_ON " (since Linux 6.9)" > > +Allow fence.i in userspace. > > "user space". > > > +.TP > > +.BR PR_RISCV_CTX_SW_FENCEI_OFF " (since Linux 6.9)" > > +Disallow fence.i in userspace. All threads in a process will be affected > > . > > > +when scope is set to > > +.B PR_RISCV_SCOPE_PER_PROCESS . > > +Therefore, caution must be taken -- only use this flag when you can > > Use \[em] for an em dash. Although in this case I think ':' or ';' > would be more appropriate. > > Also, I think 'only' would go better right before "when". > > > +guarantee that no thread in the process will emit fence.i from this point > > +onward. > > +.RE > > +.IP > > +The following values for > > +.IR arg3 > > +can be specified: > > +.RS > > +.TP > > +.BR PR_RISCV_SCOPE_PER_PROCESS " (since Linux 6.9)" > > +Ensure the icache of any thread in this process is coherent with > > +instruction storage upon migration. > > +.TP > > +.BR PR_RISCV_SCOPE_PER_THREAD " (since Linux 6.9)" > > +Ensure the icache of the current thread is coherent with instruction > > +storage upon migration. > > +.RE > > .\" prctl PR_SET_SECCOMP > > .TP > > .BR PR_SET_SECCOMP " (since Linux 2.6.23)" > > > > --- > > base-commit: a81e893f2b9316869e6098c3a079c30a48158092 > > change-id: 20240124-fencei_prctl-c24da2643379 > > > > Best regards, > > -- > > Charlie Jenkins <charlie@xxxxxxxxxxxx> > > Thanks for the patch! > > Have a lovely day, > Alex > > -- > <https://www.alejandro-colomar.es/> > Looking for a remote C programming job at the moment. Thank you for all of the suggestions! I will make the requested changes. - Charlie
